Send the notify in new task if calling by different UserHandle

BUG=345782
TBR=yfriedman
NOTRY=true

Review URL: https://codereview.chromium.org/175693002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252663 0039d316-1c4b-4281-b951-d872f2087c98
Remove callers of WebFrame::identifier() in favor of RenderFrame routing IDs.

BUG=314791
TEST=No behavior change.
R=dcheng@chromium.org

Review URL: https://codereview.chromium.org/174423003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252664 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252664