LegacyCACFLayerTreeHost was keeping this a secret, which meant that WebCore's animation
timers were never starting.

Fixes <http://webkit.org/b/53302> [Windows 7 Release Tests] changesets 76853, 76856, and
76858 broke ~36 animations, compositing, and transitions tests

Reviewed by Sam Weinig.

Source/WebCore:

* platform/graphics/ca/win/LegacyCACFLayerTreeHost.cpp:
(WebCore::LegacyCACFLayerTreeHost::contextDidChange): Call up to the base class after we
start our render timer.

LayoutTests:

Unskip compositing-related tests that are now fixed

* platform/win/Skipped:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@76968 268f45cc-cd09-0410-ab3c-d52691b4dbfc