Reviewed by John.

        Add preference for enabling the offline web application cache.
        
        * Interfaces/IWebPreferencesPrivate.idl:
        * WebPreferenceKeysPrivate.h:
        * WebPreferences.cpp:
        (WebPreferences::initializeDefaultSettings):
        (WebPreferences::setOfflineWebApplicationCacheEnabled):
        (WebPreferences::offlineWebApplicationCacheEnabled):
        * WebPreferences.h:
        * WebView.cpp:
        (WebView::notifyPreferencesChanged):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@32904 268f45cc-cd09-0410-ab3c-d52691b4dbfc