gpu: Don't send noop Flush

Don't send command buffer (shallow) Flush if the put pointer didn't advance
since the las flush.
This allows us to be safe-by-default in certain calls that go through IPC (e.g.
InsertSyncPoint or DiscardBackbuffer) by forcing a shallow flush, without
incurring a penalty if a full glFlush is needed.

BUG=None


Review URL: https://chromiumcodereview.appspot.com/12110003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@179624 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed