Refactor PluginService to take PluginList as a dependency.

webkit/plugins/npapi/plugin_list.h

Index: webkit/plugins/npapi/plugin_list.h
diff --git a/webkit/plugins/npapi/plugin_list.h b/webkit/plugins/npapi/plugin_list.h
index 847af14791042029456d0475932ff71d83c7ee8c..9eb279c7bdbf9ef7cb3efe479242539ad21d2385 100644
--- a/webkit/plugins/npapi/plugin_list.h
+++ b/webkit/plugins/npapi/plugin_list.h
@@ -126,7 +126,8 @@ class PluginList {
 
   // Returns true if the list of plugins is cached and is copied into the out
   // pointer; returns false if the plugin list needs to be refreshed.
-  bool GetPluginsIfNoRefreshNeeded(std::vector<webkit::WebPluginInfo>* plugins);
+  virtual bool GetPluginsIfNoRefreshNeeded(
+      std::vector<webkit::WebPluginInfo>* plugins);
 
   // Returns a list in |info| containing plugins that are found for
   // the given url and mime type (including disabled plugins, for