ui: Cleanup class/struct forward declarations

components/exo/surface.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_EXO_SURFACE_H_
 #define COMPONENTS_EXO_SURFACE_H_
 
 #include <list>
 #include <memory>
 #include <set>
@@ skipping 14 matching lines @@
 #include "ui/gfx/geometry/rect.h"
 
 namespace base {
 namespace trace_event {
 class TracedValue;
 }
 }
 
 namespace cc {
 class SurfaceFactory;
+class SurfaceIdAllocator;
 }
 
 namespace gfx {
 class Path;
 }
 
 namespace exo {
 class Buffer;
 class Pointer;
 class SurfaceDelegate;
@@ skipping 376 matching lines @@
 
   // Surface observer list. Surface does not own the observers.
   base::ObserverList<SurfaceObserver, true> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(Surface);
 };
 
 }  // namespace exo
 
 #endif  // COMPONENTS_EXO_SURFACE_H_