<rdar://problem/4608487> REGRESSION: reproducible crash in +[WebCoreFrameBridge supportedImageMIMETypes]

        * Plugins/WebPluginDatabase.m:
        (+[WebPluginDatabase setAdditionalWebPlugInPaths:]):
        One might be tempted to add additionalWebPlugInPaths to the global WebPluginDatabase here.
        For backward compatibility with earlier versions of the +setAdditionalWebPlugInPaths: SPI,
        we need to save a copy of the additional paths and not cause a refresh of the plugin DB
        at this time.
        (-[WebPluginDatabase _plugInPaths]):
        Include additionalWebPlugInPaths if this is the global DB.
        (-[WebPluginDatabase refresh]):
        Call -_plugInPaths to get the modified array of paths.  This is similar to what the old code
        (before we had per-WebView plugin search paths).



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@15100 268f45cc-cd09-0410-ab3c-d52691b4dbfc