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BUG=306185, 309216

Review URL: https://codereview.chromium.org/27047003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238824 0039d316-1c4b-4281-b951-d872f2087c98
Unify WebGraphicsContext3D::insertSyncPoint impls

The in-process command buffer implementation of insertSyncPoint() does
a shallow flush and returns 0 as the sync point, since the flush posts a
task which ensures ordering. The out of process implementation does additional
work in the GpuControl implementation. This moves the logic to implement
the in process version into GLES2Implementation + GpuControl instead of short
circuiting in WebGraphicsContext3DInProcessCommandBufferImpl so that callers
can use the GLES2Interface version directly.

BUG=181120

Review URL: https://codereview.chromium.org/102813003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238825 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238825