Reviewed by Darin Adler.

        Remove CanRunBeforeUnloadConfirmPanel sync message
        https://bugs.webkit.org/show_bug.cgi?id=55689

        * Shared/WebPageCreationParameters.cpp:
        (WebKit::WebPageCreationParameters::encode):
        (WebKit::WebPageCreationParameters::decode):
        Encode and decode canRunBeforeUnloadConfirmPanel, as well as canRunModal, which wasn't
        being encoded/decoded.

        * Shared/WebPageCreationParameters.h:
        Add canRunBeforeUnloadConfirmPanel.

        * UIProcess/WebPageProxy.cpp:
        (WebKit::WebPageProxy::initializeUIClient):
        Send SetCanRunBeforeUnloadConfirmPanel and SetCanRunModal messages.

        (WebKit::WebPageProxy::creationParameters):
        Initialize parameters.canRunBeforeUnloadConfirmPanel.

        * UIProcess/WebPageProxy.messages.in:
        Remove CanRunBeforeUnloadConfirmPanel message.

        * UIProcess/WebUIClient.cpp:
        (WebKit::WebUIClient::canRunBeforeUnloadConfirmPanel):
        * UIProcess/WebUIClient.h:
        Make canRunBeforeUnloadConfirmPanel const.

        * WebProcess/WebCoreSupport/WebChromeClient.cpp:
        (WebKit::WebChromeClient::canRunBeforeUnloadConfirmPanel):
        Ask the web page instead of sending a synchronous message.

        * WebProcess/WebPage/WebPage.cpp:
        (WebKit::WebPage::WebPage):
        Initialize m_canRunBeforeUnloadConfirmPanel.

        * WebProcess/WebPage/WebPage.h:
        (WebKit::WebPage::canRunBeforeUnloadConfirmPanel):
        (WebKit::WebPage::setCanRunBeforeUnloadConfirmPanel):
        Add getter and setter for m_canRunBeforeUnloadConfirmPanel.

        (WebKit::WebPage::setCanRunModal):
        Add setter for m_canRunModal.

        * WebProcess/WebPage/WebPage.messages.in:
        Add SetCanRunBeforeUnloadConfirmPanel and SetCanRunModal messages.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@80261 268f45cc-cd09-0410-ab3c-d52691b4dbfc