Clean up plug-in placeholders:

webkit/plugins/npapi/webview_plugin.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_WEBVIEW_PLUGIN_H_
 #define WEBKIT_PLUGINS_NPAPI_WEBVIEW_PLUGIN_H_
 
 #include <list>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 29 matching lines @@
     // Bind |frame| to a Javascript object, enabling the delegate to receive
     // callback methods from Javascript inside the WebFrame.
     // This method is called from WebFrameClient::didClearWindowObject.
     virtual void BindWebFrame(WebKit::WebFrame* frame) = 0;
 
     // Called before the WebViewPlugin is destroyed. The delegate should delete
     // itself here.
     virtual void WillDestroyPlugin() = 0;
 
     // Called upon a context menu event.
-    virtual void ShowContextMenu(const WebKit::WebMouseEvent&) = 0;
+    virtual void ShowContextMenu(const WebKit::WebMouseEvent&) {}
   };
 
   explicit WebViewPlugin(Delegate* delegate);
 
   // Convenience method to set up a new WebViewPlugin using |preferences|
   // and displaying |html_data|. |url| should be a (fake) chrome:// URL; it is
   // only used for navigation and never actually resolved.
   static WebViewPlugin* Create(Delegate* delegate,
                                const WebPreferences& preferences,
                                const std::string& html_data,
@@ skipping 89 matching lines @@
   std::list<std::string> data_;
   bool finished_loading_;
   scoped_ptr<WebKit::WebURLError> error_;
   WebKit::WebString old_title_;
 };
 
 }  // namespace npapi
 }  // namespace webkit
 
 #endif  // WEBKIT_PLUGINS_NPAPI_WEBVIEW_PLUGIN_H_