cc: Only trace SetNeedsManageTilesOnImplThread on positive edge

TBR=nduca@chromium.org
BUG=307821

Review URL: https://codereview.chromium.org/27463003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229042 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229042