Add initial Blink-side support for the Screen Orientation API

public/web/WebScreenOrientationClient.h

Index: public/web/WebScreenOrientationClient.h
diff --git a/public/web/WebScreenOrientationClient.h b/public/web/WebScreenOrientationClient.h
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index 0000000000000000000000000000000000000000..ea8a281fb1cc7f7e400d2dd8caf2ccd1f013b596
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+// 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 "WebScreenOrientation.h"
+
+namespace blink {
+
+class WebScreenOrientationController;
+
+class WebScreenOrientationClient {
+public:
+    virtual ~WebScreenOrientationClient() { }
+
+    virtual void lockOrientation(WebScreenOrientations) = 0;
+    virtual void unlockOrientation() = 0;
+
+    virtual void setController(WebScreenOrientationController*) = 0;
+};
+
+} // namespace blink
+
+#endif // WebScreenOrientationClient_h