blimp: Cleanup class/struct forward declarations

blimp/client/public/contents/blimp_contents.h

 // Copyright 2016 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 BLIMP_CLIENT_PUBLIC_CONTENTS_BLIMP_CONTENTS_H_
 #define BLIMP_CLIENT_PUBLIC_CONTENTS_BLIMP_CONTENTS_H_
 
 #include "base/macros.h"
 #include "base/supports_user_data.h"
 #include "ui/gfx/native_widget_types.h"
 
 #if defined(OS_ANDROID)
 #include "base/android/scoped_java_ref.h"
 #endif
 
-namespace cc {
-class Layer;
-}  // namespace cc
-
 namespace blimp {
 namespace client {
 
 class BlimpContentsObserver;
 class BlimpContentsView;
 class BlimpNavigationController;
 
 // BlimpContents is the core class in blimp client which is responsible for
 // rendering web pages in a rectangular area. The interaction with between the
 // client and engine is encapsulated behind this interface through the use of
@@ skipping 28 matching lines @@
   BlimpContents() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BlimpContents);
 };
 
 }  // namespace client
 }  // namespace blimp
 
 #endif  // BLIMP_CLIENT_PUBLIC_CONTENTS_BLIMP_CONTENTS_H_