Reduce and delay calls to StatisticsProvider that might block

BUG=302798
R=xiyuan@chromium.org

Review URL: https://codereview.chromium.org/25494004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226552 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226552