Disabling flaky RunMultiThread_DelegatingRenderer_ImplSidePaint.

Failing flakily on win/mac/linux.

Build log: http://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%281%29/builds/23746
Flakiness dashboard: http://test-results.appspot.com/dashboards/flakiness_dashboard.html#group=%40ToT%20Chromium&testType=cc_unittests&tests=LayerTreeHostTestStartPageScaleAnimation.RunMultiThread_DelegatingRenderer_ImplSidePaint

BUG=308435
R=powei
TBR=powei

Review URL: https://codereview.chromium.org/26497008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229087 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229087