[Qt] Switch ContextMenu implementation to CROSS_PLATFORM_CONTEXT_MENU
https://bugs.webkit.org/show_bug.cgi?id=113535

Reviewed by Simon Hausmann.

Source/WebCore:

Now Qt uses the CROSS_PLATFORM_CONTEXT_MENUS
USE flag. This flag provides a full cross-platform
representation of a ContextMenu and a ContextMenuItem.
The embedder can then decide how to show this, so neither
WebCore nor WebCore/platform need to know any platform
specifics about menus.

No new tests, no behavior changes.

* Target.pri:
* platform/ContextMenu.h:
(ContextMenu):
* platform/ContextMenuItem.h:
* platform/qt/ContextMenuItemQt.cpp:
(WebCore::ContextMenuItem::platformContextMenuItem):
* platform/qt/ContextMenuQt.cpp:
(WebCore::ContextMenu::ContextMenu):
(WebCore::ContextMenu::getContextMenuItems):
(WebCore::ContextMenu::createPlatformContextMenuFromItems):
(WebCore::ContextMenu::platformContextMenu):

Source/WebKit/qt:

Adjust ContextMenuClientQt and QWebPageAdapter to use CROSS_PLATFORM_CONTEXT_MENUS
USE flag by implementing customizeMenu() instead of getCustomMenuFromDefaultItems()
and by calling menu->items() instead of menu->platformDescription().

* WebCoreSupport/ContextMenuClientQt.cpp:
(WebCore::ContextMenuClientQt::customizeMenu):
* WebCoreSupport/ContextMenuClientQt.h:
(ContextMenuClientQt):
* WebCoreSupport/QWebPageAdapter.cpp:
(descriptionForPlatformMenu):
(QWebPageAdapter::updatePositionDependentMenuActions):

Tools:

Adding USE_CROSS_PLATFORM_CONTEXT_MENUS to WEBKIT_CONFIG.

* qmake/mkspecs/features/features.prf:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147545 268f45cc-cd09-0410-ab3c-d52691b4dbfc