Re-land "Pass RenderFrameHost to WebContentObservers' message handlers"
This patch enables WebContentsObserver::OnMessageReceived to receive
a reference to RenderFrameHost that received the message.
This allows passing of JavaBridgeDispatcherHostManager ownership from
WebContentsImpl to ContentViewCore and removing of some redundant
initialization code in JavaBridgeDispatcherHostManager, fixing
a long-standing TODO.
This patch also includes a fix for "Search Google for this image"
discovered shorly after the original patch has been landed.
BUG=371296
TBR=jam@chromium.org,benm@chromium.org,yoz@chromium.org,bauerb@chromium.org,fsamuel@chromium.org
Review URL: https://codereview.chromium.org/
275873002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269571 0039d316-1c4b-4281-b951-d872f2087c98