Refactor AccelerometerReader to provide an Observer

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"
@@ skipping 27 matching lines @@
     // Scale of accelerometers (i.e. raw value * scale = m/s^2).
     float scale[ui::ACCELEROMETER_SOURCE_COUNT][3];
 
     // Index of each accelerometer axis in data stream.
     int index[ui::ACCELEROMETER_SOURCE_COUNT][3];
   };
   typedef base::RefCountedData<ConfigurationData> Configuration;
   typedef base::RefCountedData<char[12]> Reading;
 
   // An interface to receive data from the AccelerometerReader.
-  class Delegate {
+  class Observer {
    public:
-    virtual ~Delegate() {}
+    virtual void OnAccelerometerUpdated(
+        const ui::AccelerometerUpdate& update) = 0;
 
-    virtual void HandleAccelerometerUpdate(
-        const ui::AccelerometerUpdate& update) = 0;
+   protected:
+    virtual ~Observer() {}
   };
 
-  AccelerometerReader(scoped_refptr<base::TaskRunner> blocking_task_runner,
-                      Delegate* delegate);
+  AccelerometerReader();
   ~AccelerometerReader();
 
+  void Initialize(scoped_refptr<base::TaskRunner> blocking_task_runner);
+
+  // Add/Remove observers.
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
  private:
   // 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_;
 
-  // A weak pointer to the delegate to send accelerometer readings to.
-  Delegate* delegate_;
-
   // The last seen accelerometer data.
   ui::AccelerometerUpdate update_;
 
   // The accelerometer configuration.
   scoped_refptr<Configuration> configuration_;
 
+  ObserverList<Observer, true> observers_;
+
   base::WeakPtrFactory<AccelerometerReader> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AccelerometerReader);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_