ui: Cleanup class/struct forward declarations

cc/surfaces/surface_resource_holder.cc

Index: cc/surfaces/surface_resource_holder.cc
diff --git a/cc/surfaces/surface_resource_holder.cc b/cc/surfaces/surface_resource_holder.cc
index ec794895906df17276fd4d4d287609adcb6e3a20..6d1e60d0c6a2766a930335eccacf382e5de2c1ec 100644
--- a/cc/surfaces/surface_resource_holder.cc
+++ b/cc/surfaces/surface_resource_holder.cc
@@ -19,6 +19,10 @@ SurfaceResourceHolder::ResourceRefs::ResourceRefs()
     : refs_received_from_child(0), refs_holding_resource_alive(0) {
 }
 
+void SurfaceResourceHolder::Reset() {
+  resource_id_info_map_.clear();
+}
+
 void SurfaceResourceHolder::ReceiveFromChild(
     const TransferableResourceArray& resources) {
   for (TransferableResourceArray::const_iterator it = resources.begin();