[GTK] Provide convenience API in DOM bindings to post messages to user message handlers
https://bugs.webkit.org/show_bug.cgi?id=138871

Patch by Adrian Perez de Castro <aperez@igalia.com> on 2014-11-20
Reviewed by Carlos Garcia Campos.

Source/WebCore:

Adds a convenience function in the WebKitGTK+ DOM bindings to post
messages to user message handlers in a way convenient way more
convenient than using the autogenerated bindings.

* bindings/gobject/WebKitDOMCustom.cpp:
(webkit_dom_dom_window_webkit_message_handlers_post_message):
Added new convenience API function to post messages to user message
handlers.
* bindings/gobject/WebKitDOMCustom.h: Ditto.
* bindings/gobject/WebKitDOMCustom.symbols: Ditto.

Tools:

Add a test case for the convenience API for posting user messages
added to the DOM bindings.

* TestWebKitAPI/Tests/WebKit2Gtk/TestWebKitUserContentManager.cpp:
(testUserContentManagerMessageFromConvenienceDOMBindings):
(beforeAll):
* TestWebKitAPI/Tests/WebKit2Gtk/WebExtensionTest.cpp:
(documentLoadedCallback):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@176393 268f45cc-cd09-0410-ab3c-d52691b4dbfc