Overhaul tracing_ui to use XHR and new tracing_controller

Based on https://codereview.chromium.org/24355002/
Pairs with https://codereview.appspot.com/23860046/

Roll trace-viewer to r1063 to include the paired change.

BUG=trace-viewer:420

Review URL: https://codereview.chromium.org/64553013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236404 0039d316-1c4b-4281-b951-d872f2087c98
Kick the pump when allowing nestable tasks on a message loop

BUG=318998

Review URL: https://codereview.chromium.org/65173003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236405 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236406 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236406
Modify scroll events when sticky keys is enabled.

To unit tests for this feature, this patch also refactors test code for
generating X events.

BUG=308662
TEST=new unit tests

Review URL: https://codereview.chromium.org/66843017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236407 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236407