[BlackBerry] Clean up BackingStoreClient (part II)

https://bugs.webkit.org/show_bug.cgi?id=99327

Reviewed by Yong Li.
Patch by Antonio Gomes <agomes@rim.com>

Remove more unneeded BackingStoreClient <-> WebPageClient integration
methods:
- BackingStoreClient* backingStoreClientForFrame(...)
- void addBackingStoreClientForFrame(...)
- void removeBackingStoreClientForFrame(...)

Change places calling WPPriv::backingStoreClientForFrame to directly
access WPPriv::backingStoreClient instead, since only the main frame will
have a BackingStoreClient instance associated with it, and it is owned by
the WKPriv.

Remove non-mainframe only references to BackingStoreClient completely,
since it is dead code now.

* Api/InRegionScroller.cpp:
(BlackBerry::WebKit::InRegionScrollerPrivate::setLayerScrollPosition):
* Api/WebPage.cpp:
(BlackBerry::WebKit::WebPagePrivate::backingStoreClient):
(BlackBerry::WebKit::WebPage::destroy):
* Api/WebPage_p.h:
(WebPagePrivate):
* WebCoreSupport/ChromeClientBlackBerry.cpp:
(WebCore::ChromeClientBlackBerry::invalidateContentsForSlowScroll):
(WebCore::ChromeClientBlackBerry::scroll):
* WebCoreSupport/FrameLoaderClientBlackBerry.cpp:
(WebCore::FrameLoaderClientBlackBerry::transitionToCommittedForNewPage):
(WebCore::FrameLoaderClientBlackBerry::createFrame):
(WebCore::FrameLoaderClientBlackBerry::detachedFromParent2):
* WebKitSupport/BackingStoreClient.cpp:
(BlackBerry::WebKit::BackingStoreClient::create):
(BlackBerry::WebKit::BackingStoreClient::BackingStoreClient):
(BlackBerry::WebKit::BackingStoreClient::~BackingStoreClient):
* WebKitSupport/BackingStoreClient.h:
(BackingStoreClient):
* WebKitSupport/InputHandler.cpp:
(BlackBerry::WebKit::InputHandler::setBatchEditingActive):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@131314 268f45cc-cd09-0410-ab3c-d52691b4dbfc