Implement DeviceMotionEvent API

chromeos/accelerometer/accelerometer_reader.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 CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_
 #define CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
-#include "base/observer_list.h"
+#include "base/observer_list_threadsafe.h"
 #include "chromeos/accelerometer/accelerometer_types.h"
 #include "chromeos/chromeos_export.h"
 
 template <typename T>
 struct DefaultSingletonTraits;
 
 namespace base {
 class TaskRunner;
 }
 
@@ skipping 22 matching lines @@
 
     // Index of each accelerometer axis in data stream.
     int index[ACCELEROMETER_SOURCE_COUNT][3];
   };
   typedef base::RefCountedData<ConfigurationData> Configuration;
   typedef base::RefCountedData<char[12]> Reading;
 
   // An interface to receive data from the AccelerometerReader.
   class Observer {
    public:
-    virtual void OnAccelerometerUpdated(const AccelerometerUpdate& update) = 0;
+    virtual void OnAccelerometerUpdated(
+        scoped_refptr<const AccelerometerUpdate> update) = 0;
 
    protected:
     virtual ~Observer() {}
   };
 
   static AccelerometerReader* GetInstance();
 
   void Initialize(scoped_refptr<base::TaskRunner> blocking_task_runner);
 
   // Add/Remove observers.
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
+  bool HasObserver(Observer* observer);
+
+  // The delay between reads of the accelerometer.
+  int DelayBetweenReadsMs() const;

[flackr, 2015/03/05 19:59:45]

Until we resolve increasing the update rate, I think we should just expose the
constant in the header like this:
https://code.google.com/p/chromium/codesearch#chromium/src/ash/wm/overview/wi...

[jonross, 2015/03/05 21:13:39]

Done.

 
  protected:
   AccelerometerReader();
   virtual ~AccelerometerReader();
 
  private:
   friend struct DefaultSingletonTraits<AccelerometerReader>;
 
   // Dispatched when initialization is complete. If |success|, |configuration|
   // provides the details of the detected accelerometer.
   void OnInitialized(scoped_refptr<Configuration> configuration, bool success);
 
   // Triggers an asynchronous read from the accelerometer, signalling
   // OnDataRead with the result.
   void TriggerRead();
 
   // If |success|, converts the raw reading to an AccelerometerUpdate
   // message and notifies the |delegate_| with the new readings.
   // Triggers another read from the accelerometer at the current sampling rate.
   void OnDataRead(scoped_refptr<Reading> reading, bool success);
 
   // The task runner to use for blocking tasks.
   scoped_refptr<base::TaskRunner> task_runner_;
 
   // The last seen accelerometer data.
-  AccelerometerUpdate update_;
-
-  // True if a valid accelerometer update is available.
-  bool has_update_;
+  scoped_refptr<AccelerometerUpdate> update_;
 
   // The accelerometer configuration.
   scoped_refptr<Configuration> configuration_;
 
-  ObserverList<Observer, true> observers_;
+  scoped_refptr<ObserverListThreadSafe<Observer>> observers_;
 
   base::WeakPtrFactory<AccelerometerReader> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AccelerometerReader);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_