Part of <rdar://problem/5471308> - Get async Icon Database fully hooked up on Windows
        
        Hook up main thread delivery of Icon Database notifications from the secondary thread
        
        * WebIconDatabase.cpp:
        (WebIconDatabase::WebIconDatabase): Initialize m_deliveryRequested
        (WebIconDatabase::init): Set the IconDatabaseClient to the shared WebIconDatabase
        (WebIconDatabase::dispatchDidRemoveAllIcons): Queue the notification to be delivered on the main thread then
          ask for the delivery
        (WebIconDatabase::dispatchDidAddIconForPageURL): Ditto
        (WebIconDatabase::scheduleNotificationDelivery): If the m_deliveryRequested hasn't been set, then set it
          and perform the callOnMainThread() for WebIconDatabase::deliverNotifications
        (postDidRemoveAllIconsNotification):
        (postDidAddIconNotification):
        (WebIconDatabase::deliverNotifications): Deliver all notifications in the current queue
        * WebIconDatabase.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@25631 268f45cc-cd09-0410-ab3c-d52691b4dbfc