investigate use of 'mac' and 'win' as fully-specified port names for the apple ports

investigate use of 'mac' and 'win' as fully-specified port names for the apple ports
https://bugs.webkit.org/show_bug.cgi?id=76475

Reviewed by Eric Seidel.

This patch cleans up the internal usage of port names for the
Apple mac and Apple win ports so that 'mac' and 'win are never
considered "fully specified" port names: they are still legal
input to the PortFactory.get() routine, but only if run on the given
platform (i.e. trying to PortFactory.get('mac') on windows or
linux will return an error, since we don't know which version of
the port is desired.

This also cleans up handling of the webkit2 variants, so that
the full port names consistently follow the
<operating_system>-<version>[-<wk2>] convention.

Lastly this patch adds some assertions and removes some
try/catch logic to catch more programming and usage errors;
previously mac-tiger might've been allowed -- and it would've
translated into using just the baselines in platform/mac -- but
now it should fail.

* Scripts/webkitpy/layout_tests/port/apple.py:
(ApplePort.determine_full_port_name):
(ApplePort.__init__):
(ApplePort):
(ApplePort._port_name_with_version):
* Scripts/webkitpy/layout_tests/port/builders.py:
* Scripts/webkitpy/layout_tests/port/factory_unittest.py:
(FactoryTest.test_mac):
(FactoryTest.test_win):
* Scripts/webkitpy/layout_tests/port/mac.py:
(MacPort.baseline_search_path):
* Scripts/webkitpy/layout_tests/port/mac_unittest.py:
(MacTest.test_versions):
* Scripts/webkitpy/layout_tests/port/win.py:
(WinPort.baseline_search_path):
* Scripts/webkitpy/layout_tests/port/win_unittest.py:
(WinTest.test_versions):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@105951 268f45cc-cd09-0410-ab3c-d52691b4dbfc