Remove content::BrowserThread knowledge from Device Sensors

content/browser/device_sensors/device_sensor_service.h

 // 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.
 
 #ifndef CONTENT_BROWSER_DEVICE_SENSORS_DEVICE_SENSOR_SERVICE_H_
 #define CONTENT_BROWSER_DEVICE_SENSORS_DEVICE_SENSOR_SERVICE_H_
 
 #include <memory>
 
 #include "base/callback_forward.h"
@@ skipping 12 matching lines @@
 // Owns the data fetcher for Device Motion and Orientation and keeps track of
 // the number of consumers currently using the data. The data fetcher is stopped
 // when there are no consumers.
 class CONTENT_EXPORT DeviceSensorService {
  public:
   // Returns the DeviceSensorService singleton.
   static DeviceSensorService* GetInstance();
 
   // Increments the number of users of the provider. The Provider is running
   // when there's > 0 users, and is paused when the count drops to 0.
-  // Must be called on the I/O thread.
+  // Must be called on a thread that can perform I/O.
   void AddConsumer(ConsumerType consumer_type);
 
   // Removes a consumer. Should be matched with an AddConsumer call.
-  // Must be called on the I/O thread.
+  // Must be called on a thread that can perform I/O.
   void RemoveConsumer(ConsumerType cosumer_type);
 
   // Returns the shared memory handle of the device motion data.
   mojo::ScopedSharedBufferHandle GetSharedMemoryHandle(
       ConsumerType consumer_type);
 
-  // Stop/join with the background polling thread in |provider_|.
-  void Shutdown();
+  // Stop/join with the background polling thread in |provider_|. Must be
+  // called on the UI thread.
+  void ShutDownOnUIThread();
 
   // Injects a custom data fetcher for testing purposes. This class takes
   // ownership of the injected object.
   void SetDataFetcherForTesting(DataFetcherSharedMemory* test_data_fetcher);
 
  private:
   friend struct base::DefaultSingletonTraits<DeviceSensorService>;
 
   DeviceSensorService();
   virtual ~DeviceSensorService();
 
   bool ChangeNumberConsumers(ConsumerType consumer_type, int delta);
   int GetNumberConsumers(ConsumerType consumer_type) const;
 
   int num_light_readers_;
   int num_motion_readers_;
   int num_orientation_readers_;
   int num_orientation_absolute_readers_;
   bool is_shutdown_;
   std::unique_ptr<DataFetcherSharedMemory> data_fetcher_;
-  base::ThreadChecker thread_checker_;
+
+  // Associated with the IO thread.
+  base::ThreadChecker io_thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(DeviceSensorService);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DEVICE_SENSORS_DEVICE_SENSOR_SERVICE_H_