Move PluginPrefs to use PluginService instead of PluginList.

content/browser/plugin_service.cc

Index: content/browser/plugin_service.cc
diff --git a/content/browser/plugin_service.cc b/content/browser/plugin_service.cc
index b0cbb7f8541d197993ecd71711b38af3b7b4d640..eb82c1f6c082ab669e37f75111e8a9d669cfcd45 100644
--- a/content/browser/plugin_service.cc
+++ b/content/browser/plugin_service.cc
@@ -643,10 +643,6 @@ void PluginService::UnregisterInternalPlugin(const FilePath& path) {
   plugin_list()->UnregisterInternalPlugin(path);
 }
 
-webkit::npapi::PluginList* PluginService::plugin_list() {
-  return webkit::npapi::PluginList::Singleton();
-}
-
 void PluginService::SetPluginListForTesting(
     webkit::npapi::PluginList* plugin_list) {
   plugin_list_ = plugin_list;