CC: Account for memory assigned to raster tasks.

Rasters are already throttled by a transfer buffer limit.
This applies the same limit in TileManager which should have
several advantages:
- We keep more content cached (raster tasks take from cache)
- The memory spike due to priority changes is minimized.
- Time spent in ScheduleTasks is much reduced.

BUG=303397

Review URL: https://codereview.chromium.org/26654008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233731 0039d316-1c4b-4281-b951-d872f2087c98
Cast: Add convergence test to congestion control.

Review URL: https://codereview.chromium.org/48523005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233732 0039d316-1c4b-4281-b951-d872f2087c98
Added UMA to track data reduction proxy probe URL and fallback

This change adds UMA to track the outcome of probing a canary
URL and adds UMA to track events that leads to the proxy being
bypassed.

BUG=314150

Review URL: https://codereview.chromium.org/52803010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233733 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233732
Scheduler: Switch from high to low latency mode if possible.

Detect if the renderer's impl thread is one frame behind the main thread (i.e. the main thread is in a high
latency mode). If, based on our estimates, the main thread can produce a new tree
before the impl thread's deadline, skip a BeginMainFrame to let the impl thread
catch up and operate in low latency mode from then on.

This feature is currently disabled by default.

BUG=309648

Review URL: https://codereview.chromium.org/54913003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233734 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233734