Remove DisableCompositingQueryAsserts from Interals.cpp

We need to update compositing before poking the animation engine.

BUG=343760

Review URL: https://codereview.chromium.org/170713003

git-svn-id: svn://svn.chromium.org/blink/trunk@167437 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fire canplaythrough after play and playing when autoplaying

The new test case is copied (with style adjustments) from
https://github.com/w3c/web-platform-tests/pull/636

Once it is imported under LayoutTests/w3c/web-platform-tests/ it should
be removed from LayoutTests/media/W3C/.

BUG=344531

Review URL: https://codereview.chromium.org/169223003

git-svn-id: svn://svn.chromium.org/blink/trunk@167438 bbb929c8-8fbe-4397-9dbb-9b2b20218538