Provide WebVR pose data only to the focused frame.

third_party/WebKit/Source/core/page/FocusChangedObserver.h

+// Copyright 2017 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 FocusChangedObserver_h
+#define FocusChangedObserver_h
+
+#include "core/CoreExport.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class CORE_EXPORT FocusChangedObserver : public GarbageCollectedMixin {
+ public:
+  virtual void focusedFrameChanged() = 0;
+
+ protected:
+  virtual ~FocusChangedObserver() {}
+};
+
+}  // namespace blink
+
+#endif  // FocusChangedObserver_h