Implement PollingThread for Device Motion.

content/browser/device_orientation/data_fetcher_shared_memory_android.cc

 // Copyright 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.
 
 #include "data_fetcher_shared_memory.h"
 
 #include "base/logging.h"
 #include "data_fetcher_impl_android.h"
 
 namespace content {
 
 DataFetcherSharedMemory::~DataFetcherSharedMemory() {
-  StopFetchingDeviceMotionData();
+  if (started_)
+    StopFetchingDeviceMotionData();
 }
 
 bool DataFetcherSharedMemory::NeedsPolling() {
   return false;
 }
 
 bool DataFetcherSharedMemory::FetchDeviceMotionDataIntoBuffer() {
   NOTREACHED();
   return false;
 }
 
 bool DataFetcherSharedMemory::StartFetchingDeviceMotionData(
     DeviceMotionHardwareBuffer* buffer) {
+  DCHECK(buffer);
   device_motion_buffer_ = buffer;
   return DataFetcherImplAndroid::GetInstance()->
       StartFetchingDeviceMotionData(buffer);
+  started_ = true;
 }
 
 void DataFetcherSharedMemory::StopFetchingDeviceMotionData() {
     DataFetcherImplAndroid::GetInstance()->StopFetchingDeviceMotionData();
+    started_ = false;

[piman, 2013/07/26 17:47:48]

nit: indent is wrong.

[timvolodine, 2013/07/29 12:06:25]

Done.

 }
 
 }  // namespace content