Adding test to verify FileStream.Dispose() ignores IO Related Exception in finalizer (dotnet/corefx#26921)

* Adding test to verify FileStream.Dispose() skips IO Related Exception only on finalization

* Skipping test on netfx because the behavior in netfx is different

Commit migrated from https://github.com/dotnet/corefx/commit/a15cc53eb5a4248c76bdc60beb3e31628bd8acf8

Fixing fa-IR negative currency format for test GetCurrencyNegativePatterns (dotnet/corefx#27138)

Fixes dotnet/corefx#27022 and dotnet/corefx#27127

Commit migrated from https://github.com/dotnet/corefx/commit/fe548ac62bdc46785e7e153a5f2a3de15daefd6d

Disable a SignalAndWait test so that relevant change in CoreCLR can be brought into CoreFX (dotnet/corefx#27131)

Commit migrated from https://github.com/dotnet/corefx/commit/6f06dcc32df6939e726d46ca45f8491db7967fb8

Add some pattern transformation tests (dotnet/corefx#27133)

Commit migrated from https://github.com/dotnet/corefx/commit/11182e0c4e65fb1e6fa0596ca9d991e3382c9fb2

reduce regex op code time (dotnet/corefx#26877)

* reduce regex op code time

* Use ValueListBuilder and stackalloc during op code generation

* Increasing op array size

Commit migrated from https://github.com/dotnet/corefx/commit/1eb5ddf1d0a3dbc0a221769a45d81d2a2b7fa81d

Add support for PDB Checksum debug directory entry (dotnet/corefx#26976)

Commit migrated from https://github.com/dotnet/corefx/commit/6b099e771d3b775b5cd273ec1b6fcec12ee7abbe

Merge pull request dotnet/corefx#27088 from geoffkizer/refactorloopbackserver

reorganize and cleanup some LoopbackServer code

Commit migrated from https://github.com/dotnet/corefx/commit/46267c1dbe46f0127e670ce25933ff49a5ec9d6e

Add FixedTimeEquals and other crypto helper routines as public API

Commit migrated from https://github.com/dotnet/corefx/commit/3872bafe8186a3e74cb66efa4a2835d60ed67ba2

API tweaks to match latest updates to spec (dotnet/corefx#27102)

* API tweaks to match latest updates to spec

Add a few new tests

See dotnet/corefx#25873

* Properly clear state when enumerating on Unix.
Make sure we don't include special directories in subdir processing. Add test.
Collapse helper that was only called in one place, and remove dead one.

Commit migrated from https://github.com/dotnet/corefx/commit/1c9cd8118abfa13165d88a4e660fbdcc6c2ebc4c

Fix and Enable Most ETW EventSource Tests (dotnet/corefx#27107)

Commit migrated from https://github.com/dotnet/corefx/commit/ad52ae103416ea67e30abf21c19d5d0c0cd01b11

Merge pull request dotnet/corefx#27007 from pakrym/pakrym/pipelines

Add System.IO.Pipelines API

Commit migrated from https://github.com/dotnet/corefx/commit/3c708ab64564304fed352355b52e2ea047860e4d

fix tests from merge

Commit migrated from https://github.com/dotnet/corefx/commit/b028092ce1af45e109edb0609b7b8cef42ee8a99

add response generation overloads

Commit migrated from https://github.com/dotnet/corefx/commit/6943fc7c0e92359e6335a618f6ff5ee8402af4ac

address PR feedback

Commit migrated from https://github.com/dotnet/corefx/commit/6ab005635528a03daa52ca727a4a74dcc0316830

reorganize and cleanup some LoopbackServer code

Commit migrated from https://github.com/dotnet/corefx/commit/ec6a7215bb28a061d2357d8c3874447bc575132d

Change HTTP default request version to HTTP/2 (dotnet/corefx#27079)

* change http default request version

* fix innerloop test

Commit migrated from https://github.com/dotnet/corefx/commit/f7a852f64bf20889579be70710f386a8d4802a34

More comments

Commit migrated from https://github.com/dotnet/corefx/commit/17b00a58129e659cf01a1cb6c045c400f8e0c984

Fix test project

Commit migrated from https://github.com/dotnet/corefx/commit/bb72f2e32593383ec3862d064cc8916ba5c4daa4

Enable SocketsHttpHandler cancellation support (dotnet/corefx#27029)

* Enable SocketsHttpHandler cancellation support

This change significantly improves the cancellation support in SocketsHttpHandler.  Previously we were passing the CancellationToken around to every method, eventually bottoming out in calls to the underlying Stream which then ends up passing them down to the underlying Socket.  But today Socket's support for cancellation is minimal, only doing up-front checks; if cancellation is requested during the socket operation rather than before, the request will be ignored.  Since HttpClient implements features like timeouts on top of cancellation support, it's important to do better than this.

The change implements cancellation by registering with the CancellationToken to dispose of the connection.  This will cause any reads/writes to wake up.  We then translate resulting exceptions into cancellation exceptions.  When in the main SendAsync method, we register once for the whole body of the operation until the point that we're returning the response message.  For individual operations on the response content stream, we register per operation; however, when feasible we try to avoid the registration costs by only registering if operations don't complete synchronously.  We also account for the case that on Unix, closing the connection may result in read operations waking up not with an exception but rather with EOF, which we also need to translate into cancellation when appropriate.

Along the way I cleaned up a few minor issues as well.

I also added a bunch of cancellation-related tests:
- Test cancellation occurring while sending request content
- Test cancellation occurring while receiving response headers
- Test cancellation occurring while receiving response body and using a buffered operation
- Test that all of the above are triggerable with CancellationTokenSource.Cancel, HttpClient.CancelPendingRequests, and HttpClient.Dispose
- Test cancellation occurring while receiving response body and using an unbuffered operation, either a ReadAsync or CopyToAsync on the response stream
- Test that a CancelPendingRequests doesn't affect unbuffered operations on the response stream

There are deficiencies here in the existing handlers, and tests have been selectively disabled accordingly (I also fixed a couple cases that naturally fell out of the changes I was making for SocketsHttpHandler).  SocketsHttpHandler passes now for all of them.

* Add test that Dispose doesn't cancel response stream

Commit migrated from https://github.com/dotnet/corefx/commit/53be85c2fe473fdea8c001e3d9fd81dd478b858e

Added tests for Microsoft.VisualBasic.CompilerServices.Conversions dotnet/corefx#1… (dotnet/corefx#26744)

* Added tests for Microsoft.VisualBasic.CompilerServices.Conversions dotnet/corefx#14344

* added tests for ToBoolean fro Object

Commit migrated from https://github.com/dotnet/corefx/commit/c705032f0f4f6e3d34f65cf5660e3c8ea109ad47

Update BuildTools, CoreClr, CoreFx to preview2-02513-01, preview2-26213-05, preview2-26213-06, respectively (dotnet/corefx#27093)

Commit migrated from https://github.com/dotnet/corefx/commit/b9b5b807378f7d17817749288c6b89db9694181a

Remove 'PDBC' data signature

Commit migrated from https://github.com/dotnet/corefx/commit/a3647d844791f916dff1053665bbce4574d0b8ee

Fixing pkgproj

Commit migrated from https://github.com/dotnet/corefx/commit/200bae71172c2aaae4698eb7ab5f14d72d678bea

Fix Process Start tests in outerloop on Unix.

Get the real user name in the test process, not the child process.  The outerloop tests are run with 'sudo'.  Which means by the time we are in the child process SUDO_USER will be set to 'root', since the parent test process was run with 'sudo'.

Fixes dotnet/corefx#26675

Commit migrated from https://github.com/dotnet/corefx/commit/bca11a079c914ed971b2f300b876f89a920a0398

NetCoreapp

Commit migrated from https://github.com/dotnet/corefx/commit/bb0d1299434fcaeabaecef5c602552cdcbe87359

IDuplexPipe

Commit migrated from https://github.com/dotnet/corefx/commit/82be16bb63124e8113ffb339b3d81c009996f957

T

Commit migrated from https://github.com/dotnet/corefx/commit/792c5cdda0a93f59428e58a1d830dac0c1176e87

Fix SocketsHttpHandler connection pool accounting for dropped connections (dotnet/corefx#27068)

When MaxConnectionsPerServer is set to anything other than int.MaxValue, the SocketsHttpHandler pool keeps track of the number of connections handed out, and this count is updated when a connection is disposed.  But if a response stream isn't disposed of, resulting in the connection never being disposed of, the count may never be updated.  This fix adds an HttpConnection derived type that simply adds a finalizer, making it pay-for-play when MaxConnectionsPerServer is set to something other than the default.

Commit migrated from https://github.com/dotnet/corefx/commit/ffa5db357252913c52e0cdad63c1573020185f6e

Clear initlocals in a bunch of assemblies (dotnet/corefx#26993)

* Clear initlocals in a bunch of assemblies

Sets
```XML
<ILLinkClearInitLocals>true</ILLinkClearInitLocals>
```
for the assemblies:
    - System.IO.FileSystem
    - System.IO.Pipes
    - System.Memory
    - System.Net.Http
    - System.Net.Http.WinHttpHandler
    - System.Net.NameResolution
    - System.Net.NetworkInformation
    - System.Net.Primitives
    - System.Net.Requests
    - System.Net.Security
    - System.Net.Sockets
    - System.Net.WebSockets
    - System.Net.WebSockets.Client
    - System.Net.WebSockets.WebSocketsProtocol
    - System.Private.Uri
    - System.Runtime
    - System.Runtime.Extensions

Eventually we'd ideally set the flag for the whole repo; these are just the ones I audited thus far.  In a few cases I had to make code changes to adapt, where the code was expecting stackallocs to be cleared.  I also looked at a few other projects (System.Collections, System.Runtime.Numerics) where there were more significant dependencies on clearing and I decided to leave those for later.

* Disable ILLinkClearInitLocals running on Unix until it works there

Commit migrated from https://github.com/dotnet/corefx/commit/f0a032e4a1c8a848574a5db3e69e8a6fa0aae91e

Revert Managed SNI usage flag (dotnet/corefx#27089)

Commit migrated from https://github.com/dotnet/corefx/commit/23709d07c3cb8e5c4be36ffe7f480151becc54b3

Workstation Id should be returned correctly (dotnet/corefx#27076)

* Fix workstation Id

* Tests for workstation id

* Add more test cases

Commit migrated from https://github.com/dotnet/corefx/commit/7425455ace4c7819b786c2f0b42fb630944aeef3

Merge pull request dotnet/corefx#27069 from stephentoub/cachessl

Cache SslClientAuthenticationOptions on SocketsHttpHandler pool

Commit migrated from https://github.com/dotnet/corefx/commit/a438733f09a739bfbd4b9f945ba049386858019a

Update ProjectNTfs, ProjectNTfsTestILC to beta-26213-00, beta-26213-00, respectively (dotnet/corefx#27083)

Commit migrated from https://github.com/dotnet/corefx/commit/73d8163328b17fee3d32ff295b03fab13fdb721e

Update CoreClr, CoreFx to preview2-26212-08, preview2-26213-01, respectively (dotnet/corefx#27080)

Commit migrated from https://github.com/dotnet/corefx/commit/bf5f02752633d92afcb249fe166a81ae84d59c77

Lower the default stack buffer size for calling getpwXXX_r methods.

By default, 1K is too large of a buffer to allocate on the stack.

Fixes dotnet/corefx#26959

Commit migrated from https://github.com/dotnet/corefx/commit/5cbac95f5530695a31a43e7748a4561e3a2dd32d

More PR comments

Commit migrated from https://github.com/dotnet/corefx/commit/1f7f6a2bb900b132689be5926c3fb132d7fe702d

PR Comments, temporary undo src crosscompile

Commit migrated from https://github.com/dotnet/corefx/commit/0cfbb25249dc640059d10120ae044455764cc71a

Switch from using SafeHandle for Unix enumeration (dotnet/corefx#27052)

* Switch from using SafeHandle for Unix enumeration

* Address feedback

* Fix faceplant, dispose in test.

Commit migrated from https://github.com/dotnet/corefx/commit/c9100ffc2988a0faf0e92898762a445ccb3c0e13

Project changeS

Commit migrated from https://github.com/dotnet/corefx/commit/2d44625e288fd28ba644c813a9e0d23ecfc95ddb

Pipelines RP comments

Commit migrated from https://github.com/dotnet/corefx/commit/50713cf859900e8116986e80b6d1a1da736645fc

Disable drawing test for distro Ubuntu18.04 (dotnet/corefx#27036)

* Disable drawing test for distro Ubuntu18.04

* Adding a new properties called IsUbuntu1804 and IsUbuntu1710OrHigher in PlatformDetection

Related to dotnet/corefx#27021

Commit migrated from https://github.com/dotnet/corefx/commit/4b4440b4c0fc280d3a9c09d117a1a6eafbbcb6c2

Clear Authorization Headers on Redirect (dotnet/corefx#26864)

When a user has added an Authorization header to a request via the HttpClient DefaultRequestHeaders Authorization field, ensure that header is stripped on redirect.

This change adds a method to strip Authorization headers that were set via the HttpClient DefaultRequestHeaders Authorization field, and calls that method on redirect. In addition, it adds a test to ensure that this behavior occurs as expected.

The new method ResetAuthRequestHeaders is based on the method ResetCookieRequestHeaders, which is used to reset cookie headers on redirect.

The issue also occurs in CurlHandler, but the fix is slightly different. Rather than remove the headers that have already been set, we can instead just skip them when copying over the new headers to the redirected request.

Fixes dotnet/corefx#26426

Commit migrated from https://github.com/dotnet/corefx/commit/7e6396b2bcb4d372b199cfb7b3b13e290c441124

Fix the throwing exception from ChannelReader.ReadAsync (dotnet/corefx#27070)

Commit migrated from https://github.com/dotnet/corefx/commit/20d9824ac3f877b2a72dd6a729134e0c5fd960ee

Fix HttpClientMiniStress.UnreadResponseMessage_Collectible test (dotnet/corefx#27061)

The async state machine was holding a reference to the response content object, which in turn prevented the response stream from being collected.

Commit migrated from https://github.com/dotnet/corefx/commit/6c9b62981190ae5886196f37d0f5dc614f4b0244

Update rename of ManagedHandler to SocketsHttpHandler

Commit migrated from https://github.com/dotnet/corefx/commit/a07b356e61a0a1d8e2d6d02bcc1e2062fbbd64ae

Cache SslClientAuthenticationOptions on SocketsHttpHandler pool

For the common case, we can just use a singleton cached instance with settings computed when the pool is created.  Only if it's accessed via HttpClientHandler with a server certificate callback do we need to still create an instance per request, in order to wrap the delegate to provide the expected semantics.

Commit migrated from https://github.com/dotnet/corefx/commit/911d4aff095f1c8648334d4a221c217cd09e466b

Update CoreClr, CoreFx to preview2-26212-05, preview2-26212-05, respectively (dotnet/corefx#27060)

Commit migrated from https://github.com/dotnet/corefx/commit/38ff6d112eee1b93d402521f924d9952bef98ef9

Allow RangeAttribute use to request InvariantCulture conversions. (dotnet/corefx#25918)

* Allow RangeAttribute use to request InvariantCulture conversions.

Adds a ParseLimitsInInvariantCulture that affects the interpretation of
the extrema set, and ConvertValueInInvariantCulture that affects the
interpretation of values.

Separate methods allows for e.g. a component assuming a
dot-decimal-separator culture defining a property with the attribute
(so invariant culture should be used) the use of the property is done
in a comma-decimal-separator (so the current culture should be used),
or any permutation of the two booleans.

Fixes dotnet/corefx#2648

* Skip NetFX on associated tests.

* Update tests in dotnet/corefx#25918 to work with changes from dotnet/corefx#26050

Commit migrated from https://github.com/dotnet/corefx/commit/015cf5d9832ed9d6734367c8a2e29dfa8bae4a25

fix stress response generation, and disable failing test (dotnet/corefx#27059)

Commit migrated from https://github.com/dotnet/corefx/commit/472c3d95749910ba600df296bbf01d78d7c4f6d8

Update CoreClr, CoreFx, ProjectNTfs, ProjectNTfsTestILC to preview2-26212-01, preview2-26212-01, beta-26212-00, beta-26212-00, respectively (dotnet/corefx#27053)

Commit migrated from https://github.com/dotnet/corefx/commit/241ea5372d4770a7f596adf272833aa6dd63a289

Tweak CurlHandler SSL not supported messages to be more helpful (dotnet/corefx#27043)

* Tweak CurlHandler SSL not supported messages to be more helpful

* Address PR feedback

Commit migrated from https://github.com/dotnet/corefx/commit/9cde3e174b2495cbcdf95995aea0bea4030d4aa9

Ensure services get removed (dotnet/corefx#27054)

Commit migrated from https://github.com/dotnet/corefx/commit/744c4cf021c1744082e12caf3e9b8dacf05a671a

Merge pull request dotnet/corefx#26989 from geoffkizer/fixcookiehandling

SocketsHttpHandler: Fix some issues with cookie handling, and add cookie tests

Commit migrated from https://github.com/dotnet/corefx/commit/8cee267154ef9dc6dde7a76a828844a200437872

acutal -> actual (dotnet/corefx#27050)

Commit migrated from https://github.com/dotnet/corefx/commit/36a15af564c8359881da9f98a7011a89253c0847

Modified Dns.GetHostAddressesAsync to be truly async (dotnet/corefx#26850)

* Modified Dns.GetHostAddressesAsync to be truly async

* Applied code review recommendations

* Unix build fix

* Unix build fix dotnet/corefx#2

* Unix build fix dotnet/corefx#3

* NETFX build fix

* Fixed useGetHostByName logic

* Simplified ProcessResult code

* Cleaned up cancel code

* cleanup

Commit migrated from https://github.com/dotnet/corefx/commit/d3ff31e3b9e8c7b1e6003196650bae4a658ef889

fix tests on netfx

Commit migrated from https://github.com/dotnet/corefx/commit/c7cc2a879d0a5b5f039caff36bef0c99f52604a2

consolidate cookie tests

Commit migrated from https://github.com/dotnet/corefx/commit/c20262c69a93449498d511014e9e69bad18f987a

Update CoreClr, CoreFx to preview2-26211-03, preview2-26211-04, respectively (dotnet/corefx#27041)

Commit migrated from https://github.com/dotnet/corefx/commit/14185df4430c7f9432ea4654676c7663c5f8957e

Add SocketsHttpHandler check for TransferEncodingChunked w/o Content (dotnet/corefx#27040)

Commit migrated from https://github.com/dotnet/corefx/commit/bf5a3183bc901723ebe0bb3d178bec86cda57429

Fix more new T[0] to be Array.Empty<T>() (dotnet/corefx#27042)

We've done several passes through the repo in the past.  More cases have snuck in since then.

Commit migrated from https://github.com/dotnet/corefx/commit/a127f01141ff4ffe2224da9ff63a1b5233ee5f06

Fix some license headers across the repo (dotnet/corefx#27039)

Commit migrated from https://github.com/dotnet/corefx/commit/7f19e761b7400521030707df2e6fac10daa36f26

Mark {Configured}ValueTaskAwaiter as readonly in contracts (dotnet/corefx#27030)

Commit migrated from https://github.com/dotnet/corefx/commit/4ff3c791c0eac88d96f135b16fc5425d48e02211

Add tests for T[] -> ArraySegment<T> cast (dotnet/corefx#27032)

Commit migrated from https://github.com/dotnet/corefx/commit/d690bb63b15556190fad7e6bb85eb7a4dce69c79

Update BuildTools to preview2-02511-02 (dotnet/corefx#27034)

Commit migrated from https://github.com/dotnet/corefx/commit/f54ee41039db4b84fb5dc58bec4e1dd393fc2d0b

Fixing test CurrencyNegativePattern_Get() on newly added distro Ubuntu18.04 (dotnet/corefx#27035)

From class/project System.Globalization.Tests.NumberFormatInfoCurrencyNegativePattern

Fixes dotnet/corefx#27022

Commit migrated from https://github.com/dotnet/corefx/commit/8fdf896ebb78fcab5612de7a0ea84518d416d7c7

Fix TestService shutdown (dotnet/corefx#27028)

Commit migrated from https://github.com/dotnet/corefx/commit/2af251c3c083817975d76d659069400d98073965

Update CoreClr to preview2-26210-06 (dotnet/corefx#27026)

Commit migrated from https://github.com/dotnet/corefx/commit/530385c33afaf373ae28f5ab49cf5c0d902dda3e

clasname -> classname (dotnet/corefx#27025)

Commit migrated from https://github.com/dotnet/corefx/commit/08bcfb4b95ec4be00ce70eb985682aca8aec8fe9

Fix *Info classes for Unix when opened on root (dotnet/corefx#27024)

Commit migrated from https://github.com/dotnet/corefx/commit/5349873018e481a2ad8a14bbdd5ff237780f02e3

Update CoreClr to preview2-26210-04 (dotnet/corefx#27020)

Commit migrated from https://github.com/dotnet/corefx/commit/221950b31c1057b040670936519ddbc13f893062

Add FileStream tests for custom OwnedMemory with Read/WriteAsync (dotnet/corefx#26931)

Commit migrated from https://github.com/dotnet/corefx/commit/7130581c8bd7114143628679624f7ae29cb56818

Add Hebrew Months test (dotnet/corefx#26915)

* Add Hebrew Months test

* add some spaces

Commit migrated from https://github.com/dotnet/corefx/commit/57ba13cbfa203c8bc5003dd9b3ab4aaa796c22f8

Update BuildTools, CoreClr, CoreFx, CoreSetup, ProjectNTfs, ProjectNTfsTestILC to preview2-02509-01, preview2-26209-08, preview2-26210-01, preview2-26209-04, beta-26209-02, beta-26209-02, respectively (dotnet/corefx#26940)

Commit migrated from https://github.com/dotnet/corefx/commit/1fc770a6cbc26dc072a44ee9ae6e6d9af5e61e1c

Fix Unix enumeration (dotnet/corefx#27019)

For non-trivial recursive enumerations we were running out of file descriptors. Stop creating them when we queue pending subdirectories and only create when we dequeue.

Commit migrated from https://github.com/dotnet/corefx/commit/430de8f582afb111697dd1e203f5c7a20f46acb2

Restrict the Long Running option to MARS (dotnet/corefx#27010)

* Restrict the Long Running option to MARS

* Code review comments

Commit migrated from https://github.com/dotnet/corefx/commit/8cc3ffbea1da042f4f0ca61ad81e234630434f21

Trying to collect info about ping test failures in macOS 10.12 (dotnet/corefx#26997)

See dotnet/corefx#26358

Commit migrated from https://github.com/dotnet/corefx/commit/7406c4c12ab76df15e0fde191856860eb87166d5

Update intellisense file drop based on 2-2-2018 doc build (dotnet/corefx#27005)

Commit migrated from https://github.com/dotnet/corefx/commit/54c80d877e2f90c4973b44db5033f2cb7abf5ce2

address review feedback

Commit migrated from https://github.com/dotnet/corefx/commit/15beaca5f2062792bf4a2dd137a42d6e53f98e5e

minimal support for ManagedHandler proxy configuration on Windows  (dotnet/corefx#26878)

* initial implementation

Commit migrated from https://github.com/dotnet/corefx/commit/468db63e2648f8a4c0c82d97e301e308b7887f7e

Cover

Commit migrated from https://github.com/dotnet/corefx/commit/4acf7f927ec0c132b301c79d79a6f3e5ba7d69fa

Merge pull request dotnet/corefx#26981 from MattGal/Ubuntu18

Add Ubuntu 18 to supported Linux list

Commit migrated from https://github.com/dotnet/corefx/commit/be4cdaecf9374f1addf15eb10b3bbd1dc7550ed2

Increasing OSX build timeout while we investigate the Performance hit (dotnet/corefx#27002)

Commit migrated from https://github.com/dotnet/corefx/commit/a72988c3793cc19b27e11d4599173cd0a5291b13

Resources

Commit migrated from https://github.com/dotnet/corefx/commit/c3a898a75c6fd0806631e072b4d89825dbf4ddb9

conditionsed -> conditioned (dotnet/corefx#26998)

Commit migrated from https://github.com/dotnet/corefx/commit/30f0b6323f7f4661c924b6229dbfc1fecc11cc0e

Fixing a regression introduced by the previous test fix. (dotnet/corefx#26970)

Commit migrated from https://github.com/dotnet/corefx/commit/59f5f604794e562fdc000d5dbedb53f68b7ceac7

rework cookie logic to address issues and remove CookieHandler

Commit migrated from https://github.com/dotnet/corefx/commit/7d11d419421cc9bea0b8fa3d186bb6a406cd3a4b

add protocol tests for cookie handling

Commit migrated from https://github.com/dotnet/corefx/commit/750b29bbb1433ad5d4c3727217192dddbef90eef

Make Unix filename conversion lazy (dotnet/corefx#26978)

* Make Unix filename conversion lazy

Also hook error handling.

* Address feedback

Commit migrated from https://github.com/dotnet/corefx/commit/ef0aca54454748002325b750c839dacba6ed3999

Disable Http status line test cases on CurlHandler (dotnet/corefx#26982)

Commit migrated from https://github.com/dotnet/corefx/commit/6730463bd0bb1a65e679b8a6643d611b69086b29

Refactor and tests for MS.CSharp's GetBestAccessibleType() (dotnet/corefx#26391)

* Rearrange GetBestAccessibleType to avoid repeated tests & recursion.

Keep all code for AggregateType in the first branch for AggregateType,
etc.

# Conflicts:
# src/Microsoft.CSharp/src/Microsoft/CSharp/RuntimeBinder/Semantics/Types/TypeManager.cs

* Use ContextForMemberLookup instead of BindingContext for best accessible

The BindingContext is only used for this property, which it hits
repeatedly, so just pass it in instead.

# Conflicts:
# src/Microsoft.CSharp/src/Microsoft/CSharp/RuntimeBinder/Semantics/Types/TypeManager.cs

* Don't use intermediate variables for out parameters.

If just going to assign it to something anyway.

# Conflicts:
# src/Microsoft.CSharp/src/Microsoft/CSharp/RuntimeBinder/Semantics/Types/TypeManager.cs

* Return type directly from GetBestAccessibleType()

The type passed in can never be ParameterModifierType or PointerType so
the case where false is returned can never be hit. Change to returning
the accessible type directly, and remove branches for false returns.

# Conflicts:
# src/Microsoft.CSharp/src/Microsoft/CSharp/RuntimeBinder/Semantics/Types/TypeManager.cs

* Add tests for getting best accessible type.

Commit migrated from https://github.com/dotnet/corefx/commit/ee64cb0126834cf8563d22db6fc73cdffc9ac4cd

Remove some dead branches from Microsoft.CSharp (dotnet/corefx#26370)

* Don't report constrained in AdjustMemberObject.

Never gets set, and constrained isn't meaningful when not producing IL
directly.

* Remove FieldSymbol.isAssigned

Set but never used. CS1612 is meaningless in dynamic code.

* Remove objectIsLvalue(pOptionalObject) from check field is lvalue.

This test will always pass, so the second part is all that is required.

* Move lvalue-detection into ExprField ctor

* Remove objectIsLvalue(pOptionalObject) from check property is lvalue.

This test will always pass, so the second part is all that is required.

* Move lvalue-detection into ExprProperty ctor

* Make objectIsLvalue a debug-only assertion.

Now only used in assertions, so make it an assertion method.

* Remove dead branches from TryReportLvalueFailure

Since we can now see that we can't enter the branch for properties, nor
escape the branch for fields, we can see that pObject will never be set
and isNested never true. Remove branches for those conditions.

Includes removal of ERR_ReturnNotLValue, contributes to dotnet/corefx#22470

* Remove path for isNested from ReportReadOnlyError

Never true.

Includes removal of ERR_AssgReadonlyStatic2 and ERR_AssgReadonly2,
contributes to dotnet/corefx#22470

* Inline ReportReadOnlyError and TryReportLvalueFailure

These are now very small, and CheckLvalue's logic is clearer with all
errors happening within the same switch

* Use FundamentalType to judge whether value is unsigned.

We've already obtained and branched on this value, and they suffice to
know whether the type is unsigned or not, so just infer from that.

Commit migrated from https://github.com/dotnet/corefx/commit/47a92df7f73d8570176c18a499dbdda4d9323101

Merge pull request dotnet/corefx#26964 from stephentoub/exposemanagedhandler

Expose SocketsHttpHandler

Commit migrated from https://github.com/dotnet/corefx/commit/eb892471f8691dad65ff47f5b12ddc8d378ae460

Add Ubuntu 18 to supported Linuxes

Commit migrated from https://github.com/dotnet/corefx/commit/5875a4ddad59a1bd40555af0375d3d6345a7e754

Restore Channels ReadAsync implementation (dotnet/corefx#26934)

* Restore Channels ReadAsync implementation

* Remove AutoResetAwaiter

* Add Base class  ReadAsync test

* address the feedback

Commit migrated from https://github.com/dotnet/corefx/commit/ce0de73e21635252ceffdb140d3a56c6c19bb565

Fix ProcessStartInfo tests on CentOS in Debug (dotnet/corefx#26945)

There is a bug in CentOS7.1 getpwnam_r where it returns the wrong value if you pass in a buffer that is too small to hold the data.  In Debug builds, we are purposefully passing in a buffer that is too small to test the fallback code, which is running into this OS bug.

See https://bugs.centos.org/view.php?id=7324

Fixes dotnet/corefx#26673

Commit migrated from https://github.com/dotnet/corefx/commit/03414aae30a0a90c5a54a85d79189e95f7f81ab4

Return canceled task from WaitToReadAsync even if data available (dotnet/corefx#26974)

Commit migrated from https://github.com/dotnet/corefx/commit/5cec1f3491e8eac76255e48274cadccd040caf81

Fix WebSocketProtocol test that never worked on netfx

Commit migrated from https://github.com/dotnet/corefx/commit/f6f5188044b126f3f6058ce361b060fc0b83257e

Add more SocketsHttpHandler tests

Commit migrated from https://github.com/dotnet/corefx/commit/8cb4d130bc3e8151fc72fe9494787643c7b00c4b

Expose SocketsHttpHandler

- Renames ManagedHandler to SocketsHttpHandler
- Moves a bunch of files around accordingly
- Updates System.Net.WebSockets.Client to use SocketsHttpHandler directly
- Updates System.Net.Http's tests with a reflection-based rather than TLS-based method for instantiating an HttpClientHandler backed by a SocketsHttpHandler.

Commit migrated from https://github.com/dotnet/corefx/commit/852d40e723c849e8d0c486676d40332343e12ca5

PDB Checksum Debug Directory Record Specification (dotnet/corefx#26912)

* PDB Checksum Debug Directory Record Specification

* Hash zeroed PDB ID

* Update PE-COFF.md

* Update PE-COFF.md

Commit migrated from https://github.com/dotnet/corefx/commit/d374be89418236e29ed3f88a3f622a3719242089