[chromium] Remove CCLayerTreeHostTestThreadOnly class to cleanup CCLayerTreeHostTests

[chromium] Remove CCLayerTreeHostTestThreadOnly class to cleanup CCLayerTreeHostTests
https://bugs.webkit.org/show_bug.cgi?id=90556

Reviewed by Adrienne Walker.

Currently many tests that run both single and threaded versions subclass
from CCLayerTreeHostTestThreadOnly just from copy/pasting. The class
only adds a runTestThreaded() which calls runTest(true). Many other
tests do run only in threaded mode call runTest(true) themselves, making
for an inconsistent mess.

We remove CCLayerTreeHostTestThreadOnly class, so we don't have tests
inheriting it that are not thread-only. And now all tests that are
thread-only call runTest(true) consistently.

* tests/CCLayerTreeHostTest.cpp:
(WTF::TEST_F):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121863 268f45cc-cd09-0410-ab3c-d52691b4dbfc