Provide WebVR pose data only to the focused frame.

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

Index: third_party/WebKit/Source/core/page/FocusChangedObserver.h
diff --git a/third_party/WebKit/Source/core/page/FocusChangedObserver.h b/third_party/WebKit/Source/core/page/FocusChangedObserver.h
new file mode 100644
index 0000000000000000000000000000000000000000..6a669b7673ae2ae60b15ddf2b9691367f3849846
--- /dev/null
+++ b/third_party/WebKit/Source/core/page/FocusChangedObserver.h
@@ -0,0 +1,23 @@
+// 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