Fixes to Pipe (dotnet/corefx#39390)
authorDavid Fowler <davidfowl@gmail.com>
Fri, 12 Jul 2019 15:34:36 +0000 (08:34 -0700)
committerGitHub <noreply@github.com>
Fri, 12 Jul 2019 15:34:36 +0000 (08:34 -0700)
* Fixes to Pipe
- Avoid clearing out the writing head in more cases
- Allow returning a fully consumed block even if writing is in progress if it isn't writing using the current block.
- Synchronize call to Advance

* Advance can no longer be inlined

Commit migrated from https://github.com/dotnet/corefx/commit/34765c5934c4b2f45853d323f4c87617cd2f3158


Trivial merge