Moved the following IPC messages used by the chrome NPAPI plugin installer out of content

webkit/plugins/npapi/webplugin_delegate.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WEBKIT_PLUGINS_NPAPI_WEBPLUGIN_DELEGATE_H_
 #define WEBKIT_PLUGINS_NPAPI_WEBPLUGIN_DELEGATE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 100 matching lines @@
 
   // Receives the data.
   virtual void DidReceiveManualData(const char* buffer, int length) = 0;
 
   // Indicates end of data load.
   virtual void DidFinishManualLoading() = 0;
 
   // Indicates a failure in data receipt.
   virtual void DidManualLoadFail() = 0;
 
-  // Only supported when the plugin is the default plugin.
-  virtual void InstallMissingPlugin() = 0;
-
   // Creates a WebPluginResourceClient instance and returns the same.
   virtual WebPluginResourceClient* CreateResourceClient(
       unsigned long resource_id,
       const GURL& url,
       int notify_id) = 0;
 
   // Creates a WebPluginResourceClient instance for an existing stream that is
   // has become seekable.
   virtual WebPluginResourceClient* CreateSeekableResourceClient(
       unsigned long resource_id, int range_request_id) = 0;
 };
 
 }  // namespace npapi
 }  // namespace webkit
 
 #endif  // WEBKIT_PLUGINS_NPAPI_WEBPLUGIN_DELEGATE_H_