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

content/common/plugin_list.h

Index: content/common/plugin_list.h
diff --git a/content/common/plugin_list.h b/content/common/plugin_list.h
index 1205238706bc0578553bed5f26eaf88f05bc0686..87319dabaf3b21e0720a883ad6cfc75489f5ab02 100644
--- a/content/common/plugin_list.h
+++ b/content/common/plugin_list.h
@@ -139,6 +139,13 @@ class CONTENT_EXPORT PluginList {
   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);