Add GetPluginPath() to npobject_util to avoid content/plugin/ include from npobject_stub.cc

content/plugin/plugin_thread.h

Index: content/plugin/plugin_thread.h
diff --git a/content/plugin/plugin_thread.h b/content/plugin/plugin_thread.h
index d325dd0531c32ccf7e00813588eb5518e83a5a62..5a95e99dfd5a77c54cba078d1ba3cd8e88767bbb 100644
--- a/content/plugin/plugin_thread.h
+++ b/content/plugin/plugin_thread.h
@@ -28,8 +28,6 @@ class PluginThread : public ChildThread {
   // Returns the one plugin thread.
   static PluginThread* current();
 
-  FilePath plugin_path() { return plugin_path_; }
-
  private:
   virtual bool OnControlMessageReceived(const IPC::Message& msg);
 
@@ -45,9 +43,6 @@ class PluginThread : public ChildThread {
   // The plugin module which is preloaded in Init
   base::NativeLibrary preloaded_plugin_module_;
 
-  // Points to the plugin file that this process hosts.
-  FilePath plugin_path_;
-
   DISALLOW_COPY_AND_ASSIGN(PluginThread);
 };