Implement the content/renderer and content/browser part of the Device Motion API.

content/common/device_motion_hardware_buffer.h

Index: content/common/device_motion_hardware_buffer.h
diff --git a/content/common/device_motion_hardware_buffer.h b/content/common/device_motion_hardware_buffer.h
new file mode 100644
index 0000000000000000000000000000000000000000..5e56d7929b123c8ee901d8a1ae028948c66b5852
--- /dev/null
+++ b/content/common/device_motion_hardware_buffer.h
@@ -0,0 +1,18 @@
+// Copyright (c) 2013 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_COMMON_DEVICE_MOTION_HARDWARE_BUFFER_H_
+#define CONTENT_COMMON_DEVICE_MOTION_HARDWARE_BUFFER_H_
+
+#include "content/common/shared_memory_seqlock_buffer.h"
+#include "third_party/WebKit/public/platform/WebDeviceMotionData.h"
+
+namespace content {
+
+typedef SharedMemorySeqLockBuffer<WebKit::WebDeviceMotionData>
+    DeviceMotionHardwareBuffer;
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_DEVICE_MOTION_HARDWARE_BUFFER_H_