Add a skeleton gamepad resource.

ppapi/proxy/plugin_dispatcher.h

Index: ppapi/proxy/plugin_dispatcher.h
diff --git a/ppapi/proxy/plugin_dispatcher.h b/ppapi/proxy/plugin_dispatcher.h
index 5cf19672556080f7fd6869d1fb029bab6ad6b9cb..ba464642f9b853d6b6d55417c20a1f4aabe612e5 100644
--- a/ppapi/proxy/plugin_dispatcher.h
+++ b/ppapi/proxy/plugin_dispatcher.h
@@ -34,6 +34,7 @@ class ResourceCreationAPI;
 
 namespace proxy {
 
+class GamepadResource;
 class ResourceMessageReplyParams;
 
 // Used to keep track of per-instance data.
@@ -48,6 +49,9 @@ struct InstanceData {
   // When non-NULL, indicates the callback to execute when mouse lock is lost.
   scoped_refptr<TrackedCallback> mouse_lock_callback;
 
+  // Lazily created the first time the plugin requests gamepad data.
+  scoped_refptr<GamepadResource> gamepad_resource;
+
   // Calls to |RequestSurroundingText()| are done by posted tasks. Track whether
   // a) a task is pending, to avoid redundant calls, and b) whether we should
   // actually call |RequestSurroundingText()|, to avoid stale calls (i.e.,