Customizable context menu support in WebKit2.

Reviewed by Sam Weinig.

- Adds an API-level WKContextMenuItem.
- Round trips through both the InjectedBundle client and the new PageContextMenuClient before
  actually displaying the menu.

* WebKit2.pro:
* WebKit2.xcodeproj/project.pbxproj:
* win/WebKit2.vcproj:

* Shared/API/c/WKBase.h:
* Shared/API/c/WKContextMenuItem.cpp: Added.
(WKContextMenuItemGetTypeID):
(WKContextMenuItemCreateAsAction):
(WKContextMenuItemCreateAsCheckableAction):
(WKContextMenuItemCreateAsSubmenu):
(WKContextMenuItemSeparatorItem):
(WKContextMenuItemGetTag):
(WKContextMenuItemGetType):
(WKContextMenuItemCopyTitle):
(WKContextMenuItemGetEnabled):
(WKContextMenuItemGetChecked):
(WKContextMenuCopySubmenuItems):
* Shared/API/c/WKContextMenuItem.h: Added.
* Shared/API/c/WKContextMenuItemTypes.h: Added.

* Shared/API/c/WKSharedAPICast.h:
(WebKit::toAPI):
(WebKit::toImpl):

* Shared/WebContextMenuItem.cpp:
(WebKit::WebContextMenuItem::create):
(WebKit::WebContextMenuItem::separatorItem):
(WebKit::WebContextMenuItem::submenuItemsAsImmutableArray):
* Shared/WebContextMenuItem.h:

* UIProcess/API/C/WKPage.cpp:
(WKPageSetPageContextMenuClient):
(WKPageSetPageFindClient):
(WKPageSetPageLoaderClient):
(WKPageSetPagePolicyClient):
(WKPageSetPageUIClient):
* UIProcess/API/C/WKPage.h:

* UIProcess/WebPageContextMenuClient.cpp: Added.
(WebKit::WebPageContextMenuClient::getContextMenuFromProposedMenu):
* UIProcess/WebPageContextMenuClient.h: Added.

* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::initializeContextMenuClient):
(WebKit::WebPageProxy::showContextMenu):
* UIProcess/WebPageProxy.h:
* UIProcess/WebPageProxy.messages.in:

* WebProcess/InjectedBundle/API/c/WKBundlePage.h:
* WebProcess/InjectedBundle/InjectedBundlePageContextMenuClient.cpp:
(WebKit::InjectedBundlePageContextMenuClient::getCustomMenuFromDefaultItems):
* WebProcess/InjectedBundle/InjectedBundlePageContextMenuClient.h:

* WebProcess/WebCoreSupport/WebContextMenuClient.cpp:
(WebKit::WebContextMenuClient::getCustomMenuFromDefaultItems):
* WebProcess/WebPage/WebContextMenu.cpp:
(WebKit::WebContextMenu::show):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@72024 268f45cc-cd09-0410-ab3c-d52691b4dbfc