Give embedders a chance to handle postMessage calls

Give embedders a chance to handle postMessage calls
https://bugs.webkit.org/show_bug.cgi?id=73883

Source/WebCore:

To support cross-process postMessage calls in Chromium (bug 73337), we need to intercept
postMessage calls to proxy windows. Originally we were just going to add a native event
listener on the Chromium side, but that required more changes to WebKit and was a bit of
a hack. See bug 73359 for a discuss about moving to this approach.

Patch by Karl Koscher <supersat@chromium.org> on 2012-01-03
Reviewed by Adam Barth.

Test: platform/chromium/fast/events/intercept-postmessage.html

* loader/FrameLoaderClient.h:
(WebCore::FrameLoaderClient::willCheckAndDispatchPostMessage): new method to allow the
    embedder to intercept postMessage calls
* page/DOMWindow.cpp:
(WebCore::DOMWindow::postMessageTimerFired): add a call to
    FrameLoaderClient::willCheckAndDispatchPostMessage

Source/WebKit/chromium:

Patch by Karl Koscher <supersat@chromium.org> on 2012-01-03
Reviewed by Adam Barth.

* public/WebFrameClient.h:
(WebKit::WebFrameClient::willCheckAndDispatchMessageEvent):
    interface to give the embedder a chance to handle this postMessage call
* src/FrameLoaderClientImpl.cpp:
(WebKit::FrameLoaderClientImpl::willCheckAndDispatchMessageEvent): Call
    willCheckAndDispatchMessageEvent on WebFrameClient
* src/FrameLoaderClientImpl.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@104005 268f45cc-cd09-0410-ab3c-d52691b4dbfc