Plugins: Remove left over references to chrome://plugins

chrome/renderer/plugins/chrome_plugin_placeholder.h

 // Copyright 2013 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 CHROME_RENDERER_PLUGINS_CHROME_PLUGIN_PLACEHOLDER_H_
 #define CHROME_RENDERER_PLUGINS_CHROME_PLUGIN_PLACEHOLDER_H_
 
 #include <stdint.h>
 #include <string>
 
@@ skipping 59 matching lines @@
   v8::Local<v8::Value> GetV8Handle(v8::Isolate* isolate) override;
   void ShowContextMenu(const blink::WebMouseEvent&) override;
 
   // content::RenderThreadObserver methods:
   void PluginListChanged() override;
 
   // content::ContextMenuClient methods:
   void OnMenuAction(int request_id, unsigned action) override;
   void OnMenuClosed(int request_id) override;
 
-  // Javascript callbacks:
-  // Open chrome://plugins in a new tab.
-  void OpenAboutPluginsCallback();
   // Show the Plugins permission bubble.
   void ShowPermissionBubbleCallback();
 
   // IPC message handlers:
 #if BUILDFLAG(ENABLE_PLUGIN_INSTALLATION)
   void OnDidNotFindMissingPlugin();
   void OnFoundMissingPlugin(const base::string16& plugin_name);
   void OnStartedDownloadingPlugin();
   void OnFinishedDownloadingPlugin();
   void OnErrorDownloadingPlugin(const std::string& error);
@@ skipping 18 matching lines @@
 
   int context_menu_request_id_;  // Nonzero when request pending.
   base::string16 plugin_name_;
 
   bool did_send_blocked_content_notification_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromePluginPlaceholder);
 };
 
 #endif  // CHROME_RENDERER_PLUGINS_CHROME_PLUGIN_PLACEHOLDER_H_