Adds support for calling postMessage on a frame living in a different renderer.

Patch partly from Karl Koscher <supersat@chromium.org>
BUG=99202
TEST=PostMessage calls work after navigating a window to a different process.

Review URL: https://chromiumcodereview.appspot.com/9108001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@137024 0039d316-1c4b-4281-b951-d872f2087c98
12 files changed