cc: SwapAck throttle Swap without throttling MainFrames

cc: SwapAck throttle Swap without throttling MainFrames

This should improve main thread throughput in cases
where we are deferring the BeginMainFrame, but don't
really need to because the swap ack will come back
before the impl thread needs to draw anyway.

BUG=311213
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=266685

[brianderson, 2014-04-03 02:42:01]

Depends on:
https://codereview.chromium.org/221833009
and the rest.

[Sami, 2014-04-08 13:47:32]

Thanks for splitting this out. lgtm % a simple test?

[danakj, 2014-04-15 15:42:54]

LGTM % test also

[brianderson, 2014-04-28 18:06:23]

The CQ bit was checked by brianderson@chromium.org

[commit-bot: I haz the power, 2014-04-28 18:07:35]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/brianderson@chromium.org/222023010/30001

[commit-bot: I haz the power, 2014-04-28 23:23:48]

Change committed as 266685

[Michael Achenbach, 2014-04-29 07:02:03]

A revert of this CL has been created in
https://codereview.chromium.org/255033004/ by machenbach@chromium.org.

The reason for reverting is: [Sheriff] Speculative revert for breaking win7 dbg:

http://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%28...

Will reland if it didn't help..