Reviewed by Sam Weinig.

        Change InstantiatePlugin to be asynchronous so we won't deadlock if the plug-in tries to call
        back into us while it's being instantiated.
        
        * Plugins/Hosted/NetscapePluginHostManager.mm:
        (WebKit::NetscapePluginHostManager::instantiatePlugin):
        * Plugins/Hosted/NetscapePluginHostProxy.h:
        (WebKit::NetscapePluginHostProxy::clientPort):
        * Plugins/Hosted/NetscapePluginHostProxy.mm:
        (WKPCInstantiatePluginReply):
        * Plugins/Hosted/NetscapePluginInstanceProxy.h:
        (WebKit::NetscapePluginInstanceProxy::Reply::):
        (WebKit::NetscapePluginInstanceProxy::Reply::Reply):
        (WebKit::NetscapePluginInstanceProxy::Reply::~Reply):
        (WebKit::NetscapePluginInstanceProxy::InstantiatePluginReply::InstantiatePluginReply):
        (WebKit::NetscapePluginInstanceProxy::setCurrentReply):
        (WebKit::NetscapePluginInstanceProxy::waitForReply):
        * Plugins/Hosted/NetscapePluginInstanceProxy.mm:
        (WebKit::NetscapePluginInstanceProxy::NetscapePluginInstanceProxy):
        (WebKit::NetscapePluginInstanceProxy::processRequestsAndWaitForReply):
        * Plugins/Hosted/WebKitPluginClient.defs:
        * Plugins/Hosted/WebKitPluginHost.defs:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@39324 268f45cc-cd09-0410-ab3c-d52691b4dbfc