Re-land "Pass RenderFrameHost to WebContentObservers' message handlers"

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

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=269571

[mnaganov (inactive), 2014-05-09 12:39:13]

I'm re-landing my change that had been speculatively reverted during the recent
tree firefighting, with NO CHANGES, hence TBR.

I have combined the patch with a trivial post-fix for a problem discovered
later, see https://codereview.chromium.org/274593003/ (that patch was never
landed due to tree redness).

[mnaganov (inactive), 2014-05-09 12:39:18]

The CQ bit was checked by mnaganov@chromium.org

[commit-bot: I haz the power, 2014-05-09 12:46:14]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/mnaganov@chromium.org/275873002/1

[jam, 2014-05-09 17:19:13]

lgtm

[commit-bot: I haz the power, 2014-05-10 12:06:37]

Change committed as 269571

[Evan Stade, 2016-07-16 00:06:37]

On 2014/05/10 12:06:37, commit-bot: I haz the power wrote:
> Change committed as 269571

this also broke InfoBarService (similar to CoreTabHelper). No one noticed this
rare infobar went missing for the last 2 years. :[ I wonder if any other
messages are getting dropped on the floor?