Revert 113676 - Attempt 2 at : Makes tests either use mock compositor or mock

Revert 113676 - Attempt 2 at : Makes tests either use mock compositor or mock
WebGraphicsContext3D depending upon which compositor we're
running. This is needed to enable ui tests on the bots.

I reverted first attempt as it broke some browser_tests. I've
straightened that out in another patch, so this should be good go
again. TBR since it's the same patch as before.

BUG=104360
TEST=none
TBR=ben@chromium.org

Review URL: http://codereview.chromium.org/8889022

TBR=sky@chromium.org
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=113683