Use WebViewClient instead of BlinkPlatform for screen lock.

public/platform/WebScreenOrientationClient.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 WebScreenOrientationClient_h
+#define WebScreenOrientationClient_h
+
+#include "public/platform/WebScreenOrientationLockType.h"
+
+namespace blink {
+
+class WebLockOrientationCallback;
+
+// Client handling screen orientation locking for a given WebView.
+class WebScreenOrientationClient {
+public:
+    virtual ~WebScreenOrientationClient() { }
+
+    // Request a screen orientation lock. The implementation will own the callback.
+    virtual void lockOrientation(WebScreenOrientationLockType, WebLockOrientationCallback*) = 0;
+
+    // Unlock the screen orientation. No-op if the screen orientation was not locked.
+    virtual void unlockOrientation() = 0;
+};
+
+} // namespace blink
+
+#endif // WebScreenOrientationClient_h