Repaint tests don't work in WebKit2

Repaint tests don't work in WebKit2
https://bugs.webkit.org/show_bug.cgi?id=68453

Reviewed by Sam Weinig.

Expose WKBundlePage methods to turn on repaint rect tracking
in WebKit2, for WebKitTestRunner.

As part of the change, expose utility methods on WebPage
to get the main Frame and FrameView, which required renaming
the exisiting method that returns a WebFrame. Fix callers
of that method to handle null when necessary.

* WebProcess/InjectedBundle/API/c/WKBundlePage.cpp:
(WKBundlePageGetMainFrame):
(WKBundlePageSetTracksRepaints):
(WKBundlePageIsTrackingRepaints):
(WKBundlePageResetTrackedRepaints):
(WKBundlePageCopyTrackedRepaintRects):
* WebProcess/InjectedBundle/API/c/WKBundlePagePrivate.h:
* WebProcess/WebCoreSupport/WebChromeClient.cpp:
(WebKit::findLargestFrameInFrameSet):
(WebKit::WebChromeClient::closeWindowSoon):
* WebProcess/WebCoreSupport/WebFrameLoaderClient.cpp:
(WebKit::WebFrameLoaderClient::dispatchDidFirstLayout):
(WebKit::WebFrameLoaderClient::dispatchDidLayout):
(WebKit::WebFrameLoaderClient::frameLoadCompleted):
(WebKit::WebFrameLoaderClient::restoreViewState):
(WebKit::WebFrameLoaderClient::provisionalLoadStarted):
(WebKit::WebFrameLoaderClient::transitionToCommittedFromCachedFrame):
(WebKit::WebFrameLoaderClient::transitionToCommittedForNewPage):
(WebKit::WebFrameLoaderClient::createPlugin):
* WebProcess/WebCoreSupport/mac/WebEditorClientMac.mm:
(WebKit::WebEditorClient::documentFragmentFromAttributedString):
* WebProcess/WebPage/WebFrame.cpp:
(WebKit::WebFrame::isMainFrame):
* WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::setTracksRepaints):
(WebKit::WebPage::isTrackingRepaints):
(WebKit::WebPage::resetTrackedRepaints):
(WebKit::WebPage::trackedRepaintRects):
(WebKit::WebPage::clearMainFrameName):
(WebKit::WebPage::layoutIfNeeded):
(WebKit::WebPage::mainFrameHasCustomRepresentation):
(WebKit::WebPage::mainFrame):
(WebKit::WebPage::mainFrameView):
* WebProcess/WebPage/WebPage.h:
(WebKit::WebPage::mainWebFrame):
* WebProcess/WebPage/mac/WKAccessibilityWebPageObject.mm:
(-[WKAccessibilityWebPageObject accessibilityHitTest:]):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@95968 268f45cc-cd09-0410-ab3c-d52691b4dbfc