Refactor AccelerometerReader to provide an Observer

chromeos/accelerometer/accelerometer_reader.h

Index: chromeos/accelerometer/accelerometer_reader.h
diff --git a/chromeos/accelerometer/accelerometer_reader.h b/chromeos/accelerometer/accelerometer_reader.h
index 3cf473f72cf44346c83714a3a9f2fdea6f0e4861..4754a8992339ab8bcc60b511918cc68c224b407a 100644
--- a/chromeos/accelerometer/accelerometer_reader.h
+++ b/chromeos/accelerometer/accelerometer_reader.h
@@ -45,18 +45,24 @@ class CHROMEOS_EXPORT AccelerometerReader {
   typedef base::RefCountedData<char[12]> Reading;
 
   // An interface to receive data from the AccelerometerReader.
-  class Delegate {
+  class Observer {
    public:
-    virtual ~Delegate() {}
-
-    virtual void HandleAccelerometerUpdate(
+    virtual void OnAccelerometerUpdated(
         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.
@@ -74,9 +80,6 @@ class CHROMEOS_EXPORT AccelerometerReader {
   // 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_;
 
@@ -85,6 +88,8 @@ class CHROMEOS_EXPORT AccelerometerReader {
 
   base::WeakPtrFactory<AccelerometerReader> weak_factory_;

[flackr, 2014/12/12 16:47:11]

Keep this as the last member of the class. Members are destructed in reverse
declaration order and this helps ensure that this class will not be used as soon
as it starts to be destructed.

[jonross, 2014/12/12 19:03:25]

Done.

 
+  ObserverList<Observer, true> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(AccelerometerReader);
 };