Refactor AccelerometerReader to provide an Observer

athena/system/orientation_controller.cc

 // 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.
 
 #include "athena/screen/public/screen_manager.h"
 #include "athena/system/orientation_controller.h"
 #include "base/bind.h"
 #include "base/files/file_path_watcher.h"
 #include "base/files/file_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/task_runner.h"
 
 namespace athena {
 
 namespace {
 
 // Threshold after which to rotate in a given direction.
 const int kGravityThreshold = 6.0f;
 
 }  // namespace
 
 OrientationController::OrientationController() {
 }
 
 void OrientationController::InitWith(
     scoped_refptr<base::TaskRunner> blocking_task_runner) {
-  accelerometer_reader_.reset(
-      new chromeos::AccelerometerReader(blocking_task_runner, this));
+  accelerometer_reader_.reset(new chromeos::AccelerometerReader());
+  accelerometer_reader_->Initialize(blocking_task_runner);
+  accelerometer_reader_->AddObserver(this);
 }
 
 OrientationController::~OrientationController() {
+  DCHECK_FALSE(accelerometer_reader_.get());
 }
 
 void OrientationController::Shutdown() {
+  accelerometer_reader_->RemoveObserver(this);
   accelerometer_reader_.reset();
 }
 
-void OrientationController::HandleAccelerometerUpdate(
+void OrientationController::OnAccelerometerUpdated(
     const ui::AccelerometerUpdate& update) {
   if (!update.has(ui::ACCELEROMETER_SOURCE_SCREEN))
     return;
 
   float gravity_x = update.get(ui::ACCELEROMETER_SOURCE_SCREEN).x();
   float gravity_y = update.get(ui::ACCELEROMETER_SOURCE_SCREEN).y();
   gfx::Display::Rotation rotation;
   if (gravity_x < -kGravityThreshold) {
     rotation = gfx::Display::ROTATE_270;
   } else if (gravity_x > kGravityThreshold) {
     rotation = gfx::Display::ROTATE_90;
   } else if (gravity_y < -kGravityThreshold) {
     rotation = gfx::Display::ROTATE_180;
   } else if (gravity_y > kGravityThreshold) {
     rotation = gfx::Display::ROTATE_0;
   } else {
     // No rotation as gravity threshold was not hit.
     return;
   }
 
   if (rotation == current_rotation_)
     return;
 
   current_rotation_ = rotation;
   ScreenManager::Get()->SetRotation(rotation);
 }
 
 }  // namespace athena