Fix failing browser tests when running with force-compositing-mode. It uses new trace events checke…

Fix failing browser tests when running with force-compositing-mode. It uses new trace events checked in by: http://trac.webkit.org/changeset/128785 to properly track WebGL and accelerated canvas instead of relying on
the swap-buffers calls (which get issued anyway, when in FCM). 

This patch has most of the contents of: https://codereview.chromium.org/10914247 except that it doesn't change any of the field trial probabilities.
It fixes the following tests: Canvas2DDisabled, Canvas2DBlocked, WebGLBLocked, WebGLDisabled, AcceleratedCompositingDisabled,
AcceleratedCompositingBlocked . 

It also disables ExtensionApiTest.CaptureVisibleTabJPeg as it triggers flakiness on it. chrome.tabs.captureVisibleTab is inherently racy as there is no way to guarantee that the tab has been painted at least once when that call is made. Note how the other variants of CaptureVisibleTab tests have already been disabled for similar reasons. (this was done with aa@'s advice)

BUG=155336
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=161733

[Vangelis Kokkevis, 2012-10-11 23:42:15]

This code was essentially LGTM'd in https://codereview.chromium.org/10914247

I'm now splitting the part that fixes the test failures with FCM from the field
trial percentage change.

Darin, would you mind taking a look?

[darin (slow to review), 2012-10-12 22:17:10]

LGTM

[Vangelis Kokkevis, 2012-10-12 23:34:34]

On 2012/10/12 22:17:10, darin wrote:
> LGTM

Pretty sure the chrome_frame_test failures are not mine.  They also happen with
a completely clean try: 
http://build.chromium.org/p/tryserver.chromium/builders/win_rel/builds/70144

[commit-bot: I haz the power, 2012-10-12 23:35:01]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/vangelis@chromium.org/11091072/2001

[commit-bot: I haz the power, 2012-10-13 06:06:02]

Change committed as 161733