[GTK] [WK2] Implement the policy client

[GTK] [WK2] Implement the policy client
https://bugs.webkit.org/show_bug.cgi?id=76343

Reviewed by Gustavo Noronha Silva.

Source/WebKit2:

Implement the abstract WebKitPolicyDecision, WebKitNavigationPolicyDecision,
and add the decide-policy signal to WebKitWebView.

* GNUmakefile.am: Add new files to the source list.
* UIProcess/API/gtk/WebKitError.cpp: Use the WebCore namespace because
of changes to ASSERT_MATCHING_ENUMS.
* UIProcess/API/gtk/WebKitNavigationPolicyDecision.cpp: Added.
* UIProcess/API/gtk/WebKitNavigationPolicyDecision.h: Added.
* UIProcess/API/gtk/WebKitNavigationPolicyDecisionPrivate.h: Added.
* UIProcess/API/gtk/WebKitPolicyClient.cpp: Added.
* UIProcess/API/gtk/WebKitPolicyClientPrivate.h: Added.
* UIProcess/API/gtk/WebKitPolicyDecision.cpp: Added.
* UIProcess/API/gtk/WebKitPolicyDecision.h: Added.
* UIProcess/API/gtk/WebKitPolicyDecisionPrivate.h: Added.
* UIProcess/API/gtk/WebKitPrivate.h: Modify ASSERT_MATCHING_ENUMS to make
it useful for non-WebCore enums.
* UIProcess/API/gtk/WebKitWebView.cpp:
(webkitWebViewConstructed): Attach the policy client callbacks to the page.
(webkit_web_view_class_init): Add the decide-policy signal definition.
(webkitWebViewMakePolicyDecision): Added this private method to fire the signal.
* UIProcess/API/gtk/WebKitWebView.h: Added new signal to the list.
* UIProcess/API/gtk/WebKitWebViewPrivate.h: Added new method declaration.
* UIProcess/API/gtk/docs/webkit2gtk-docs.sgml: Added new classes to the docs.
* UIProcess/API/gtk/docs/webkit2gtk-sections.txt: Ditto.
* UIProcess/API/gtk/tests/GNUmakefile.am: Added new test to the source list.
* UIProcess/API/gtk/tests/TestWebKitPolicyClient.cpp: Added.
* UIProcess/API/gtk/webkit2marshal.list: decide-policy has a new signature.

Tools:

* gtk/generate-gtkdoc:
(get_webkit2_options): Update the list of skipped source files to include all clients.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@106142 268f45cc-cd09-0410-ab3c-d52691b4dbfc