[ScreenOrientation] Fix a possible crash point in ScreenOrientationProvider.

content/public/browser/screen_orientation_provider.h

 // Copyright 2014 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 CONTENT_PUBLIC_BROWSER_SCREEN_ORIENTATION_PROVIDER_H_
 #define CONTENT_PUBLIC_BROWSER_SCREEN_ORIENTATION_PROVIDER_H_
 
-#include <memory>
-
 #include "base/callback.h"
 #include "base/macros.h"
+#include "base/optional.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "device/screen_orientation/public/interfaces/screen_orientation_lock_types.mojom.h"
 #include "third_party/WebKit/public/platform/modules/screen_orientation/WebScreenOrientationLockType.h"
 
 namespace content {
 
 class ScreenOrientationDelegate;
 class WebContents;
 
@@ skipping 43 matching lines @@
   bool LockMatchesCurrentOrientation(blink::WebScreenOrientationLockType lock);
 
   // Not owned, responsible for platform implementations.
   static ScreenOrientationDelegate* delegate_;
 
   // Whether the ScreenOrientationProvider currently has a lock applied.
   bool lock_applied_;
 
   // Locks that require orientation changes are not completed until
   // OnOrientationChange.
-
   base::Optional<blink::WebScreenOrientationLockType> pending_lock_orientation_;
 
-  LockOrientationCallback on_result_callback_;
+  LockOrientationCallback pending_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenOrientationProvider);
 };
 
 } // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_SCREEN_ORIENTATION_PROVIDER_H_