[GTK][WK2] Add document-loaded signal to WebKitWebPage
https://bugs.webkit.org/show_bug.cgi?id=110614

Patch by Manuel Rego Casasnovas <rego@igalia.com> on 2013-04-12
Reviewed by Carlos Garcia Campos.

Add a new signal document-loaded to WebKitWebPage that will be emitted
when the DOM document has been loaded for the main frame.

* UIProcess/API/gtk/tests/TestWebExtensions.cpp:
(documentLoadedCallback):
(testDocumentLoadedSignal):
(beforeAll): Add test for document-loaded signal.
* UIProcess/API/gtk/tests/WebExtensionTest.cpp:
(documentLoadedCallback):
(pageCreatedCallback):
(methodCallCallback): Add new D-Bus signal DocumentLoaded in order to
test document-loaded signal.
* WebProcess/InjectedBundle/API/gtk/WebKitWebPage.cpp:
(webkit_web_page_class_init):
(webkitWebPageCreate): Add document-loaded signal and emit it when
didFinishDocumentLoadForFrame is called.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148281 268f45cc-cd09-0410-ab3c-d52691b4dbfc