Restart plugin loading only if the plugin list has actually become stale.

content/common/plugin_list.h

 // Copyright (c) 2012 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 CONTENT_COMMON_PLUGIN_LIST_H_
 #define CONTENT_COMMON_PLUGIN_LIST_H_
 
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 121 matching lines @@
                                 std::vector<WebPluginInfo>* plugins,
                                 WebPluginInfo* plugin_info);
 
   // The following functions are used to support probing for WebPluginInfo
   // using a different instance of this class.
 
   // Computes a list of all plugins to potentially load from all sources.
   void GetPluginPathsToLoad(std::vector<base::FilePath>* plugin_paths,
                             bool include_npapi);
 
+  // Signals that plugin loading will start. This method should be called before
+  // loading plugins with a different instance of this class. Returns false if
+  // the plugin list is up to date.
+  // When loading has finished, SetPlugins() should be called with the list of
+  // plugins.
+  bool PrepareForPluginLoading();
+
   // Clears the internal list of Plugins and copies them from the vector.
   void SetPlugins(const std::vector<WebPluginInfo>& plugins);
 
   void set_will_load_plugins_callback(const base::Closure& callback);
 
   virtual ~PluginList();
 
   // Creates a WebPluginInfo structure given a plugin's path.  On success
   // returns true, with the information being put into "info".
   // Returns false if the library couldn't be found, or if it's not a plugin.
@@ skipping 91 matching lines @@
   // Flag indicating whether third_party plugins will be searched for
   // in common places.
   bool plugins_discovery_disabled_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginList);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_PLUGIN_LIST_H_