[Qt][WK2] Add support for hover API in Qt WebKit2

[Qt][WK2] Add support for hover API in Qt WebKit2
https://bugs.webkit.org/show_bug.cgi?id=68369

Reviewed by Andreas Kling.

Source/WebKit2:

Based on the patch from Igor Oliveira in the same bug.

Expose a linkHovered() signal in QDesktopWebView, that passes the QUrl and the
QString corresponding to the link title. I left textContent out because was
unsure of its use case.

In QDesktopWebView we store the last URL and title emitted to make sure we send
the signal only if either value changes. Tests were added to the QML element to
check: if values are correctly emitted and if we don't emit more signals than
necessary.

* UIProcess/API/qt/qdesktopwebview.cpp:
(QDesktopWebViewPrivate::didMouseMoveOverElement):
* UIProcess/API/qt/qdesktopwebview.h:
* UIProcess/API/qt/qdesktopwebview_p.h:
* UIProcess/API/qt/tests/qmltests/DesktopWebView/tst_linkHovered.qml: Added.
* UIProcess/API/qt/tests/qmltests/common/test2.html:
* UIProcess/API/qt/tests/qmltests/qmltests.pro:
* UIProcess/qt/ClientImpl.cpp:
(qt_wk_mouseDidMoveOverElement):
* UIProcess/qt/ClientImpl.h:
* UIProcess/qt/QtWebPageProxy.cpp:
(QtWebPageProxy::init):
* UIProcess/qt/TouchViewInterface.h:
(WebKit::TouchViewInterface::didMouseMoveOverElement):
* UIProcess/qt/ViewInterface.h:

Tools:

Change the statusbar to show the link URL when hovering links in
MiniBrowser using QDesktopWebView.

* MiniBrowser/qt/BrowserWindow.cpp:
(BrowserWindow::BrowserWindow):
(BrowserWindow::onLinkHovered):
* MiniBrowser/qt/BrowserWindow.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96105 268f45cc-cd09-0410-ab3c-d52691b4dbfc