cc: Fix disabled vsync state freezing

cc: Fix disabled vsync state freezing

Previously, when vsync was disabled the scheduler state machine would
never proactively request a new begin frame message.  This logic was
tightly coupled to commits not being aborted and causing a redraw,
incrementing the frame number, and allowing a number of the "only once
per frame" logic in the state machine to proceed.

Instead, treat disabled vsync like the synchronous compositor.  In both
cases, it's undesirable to proactively request a begin frame.  For the
synchronous compositor, this is because every begin frame results in a
draw.  For the unthrottled disabled vsync case, this is because if the
compositor can't draw it will get into a tight loop of continuing to
request new begin frames.  By lumping it with the synchronous compositor
logic, it will periodically poll to see if it needs to start a new frame
rather than freezing forever.

R=brianderson@chromium.org
BUG=303293
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=227060

[enne (OOO), 2013-10-03 20:07:03]

PTAL

[brianderson, 2013-10-03 20:17:51]

lgtm.

I like the SupportsProactiveBeginFrame abstraction. We'll want to add tests to
make sure we don't keep breaking disabled vsync, but we should really get this
fix in.

I have some ideas for how we can better support disabled vsync with the deadline
scheduler, without throttling the frame after an aborted commit, but we can take
a look at that later too.

[brianderson, 2013-10-04 15:40:05]

A useful test for this particular regression would be similar to
LayerTreeHostTestAbortedCommitDoesntStallNextCommitWhenIdle, except that instead
of setting using_synchronous_renderer_compositor to true, it could set
throttle_frame_production to false.

[brianderson, 2013-10-04 17:24:39]

Thanks for the test and avoiding test duplication. lgtm.

[commit-bot: I haz the power, 2013-10-04 17:25:05]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/enne@chromium.org/25494009/6001

[commit-bot: I haz the power, 2013-10-04 19:49:22]

Change committed as 227060