Use standardized and extendable accelerometer update type.

ui/accelerometer/accelerometer_types.cc

Index: ui/accelerometer/accelerometer_types.cc
diff --git a/ui/accelerometer/accelerometer_types.cc b/ui/accelerometer/accelerometer_types.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e5aa0ea8db83e547633a137d49120f724e332ff7
--- /dev/null
+++ b/ui/accelerometer/accelerometer_types.cc
@@ -0,0 +1,21 @@
+// 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.
+
+#include "ui/accelerometer/accelerometer_types.h"
+
+namespace ui {
+
+AccelerometerReading::AccelerometerReading() : present(false) {
+}
+
+AccelerometerReading::~AccelerometerReading() {
+}
+
+AccelerometerUpdate::AccelerometerUpdate() {
+}
+
+AccelerometerUpdate::~AccelerometerUpdate() {
+}
+
+}  // namespace ui