chrome: Cleanup class/struct forward declarations

chrome/browser/android/vr_shell/vr_shell_delegate.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 CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_DELEGATE_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_DELEGATE_H_
 
 #include <jni.h>
 
 #include "base/android/jni_weak_ref.h"
 #include "base/macros.h"
 #include "device/vr/android/gvr/gvr_delegate.h"
 
 namespace device {
 class GvrDeviceProvider;
 }
 
 namespace vr_shell {
 
-class VrShell;
-
 class VrShellDelegate : public device::GvrDelegateProvider {
  public:
   VrShellDelegate(JNIEnv* env, jobject obj);
   virtual ~VrShellDelegate();
 
   static VrShellDelegate* GetNativeDelegate(JNIEnv* env, jobject jdelegate);
 
   base::WeakPtr<device::GvrDeviceProvider> GetDeviceProvider();
 
   void SetPresentResult(JNIEnv* env, jobject obj, jboolean result);
@@ skipping 15 matching lines @@
   base::Callback<void(bool)> present_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(VrShellDelegate);
 };
 
 bool RegisterVrShellDelegate(JNIEnv* env);
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_DELEGATE_H_