Revert of Gardening: Revert "Use AudioStreamMonitor to control power save blocking."

media/audio/audio_output_controller.h

 // Copyright (c) 2012 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 MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
 
 #include "base/atomic_ref_count.h"
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/timer/timer.h"
+#include "build/build_config.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_manager.h"
 #include "media/audio/audio_power_monitor.h"
 #include "media/audio/audio_source_diverter.h"
 #include "media/audio/simple_sources.h"
 #include "media/base/media_export.h"
 
 // An AudioOutputController controls an AudioOutputStream and provides data
 // to this output stream. It has an important function that it executes
 // audio operations like play, pause, stop, etc. on a separate thread,
@@ skipping 23 matching lines @@
 // all functionally equivalent and require a Play() call to continue to the next
 // state.
 //
 // The AudioOutputStream can request data from the AudioOutputController via the
 // AudioSourceCallback interface. AudioOutputController uses the SyncReader
 // passed to it via construction to synchronously fulfill this read request.
 //
 
 namespace media {
 
-// Only do power monitoring for non-mobile platforms that need it for the UI.
-#if !defined(OS_ANDROID) && !defined(OS_IOS)
-#define AUDIO_POWER_MONITORING
-#endif
-
 class MEDIA_EXPORT AudioOutputController
     : public base::RefCountedThreadSafe<AudioOutputController>,
       public AudioOutputStream::AudioSourceCallback,
       public AudioSourceDiverter,
       NON_EXPORTED_BASE(public AudioManager::AudioDeviceListener)  {
  public:
   // An event handler that receives events from the AudioOutputController. The
   // following methods are called on the audio manager thread.
   class MEDIA_EXPORT EventHandler {
    public:
@@ skipping 33 matching lines @@
   // thread, and if this is successful, the |event_handler| will receive an
   // OnCreated() call from the same audio manager thread.  |audio_manager| must
   // outlive AudioOutputController.
   // The |output_device_id| can be either empty (default device) or specify a
   // specific hardware device for audio output.
   static scoped_refptr<AudioOutputController> Create(
       AudioManager* audio_manager, EventHandler* event_handler,
       const AudioParameters& params, const std::string& output_device_id,
       SyncReader* sync_reader);
 
+  // Indicates whether audio power level analysis will be performed.  If false,
+  // ReadCurrentPowerAndClip() can not be called.
+  static bool will_monitor_audio_levels() {
+#if defined(OS_ANDROID) || defined(OS_IOS)
+    return false;
+#else
+    return true;
+#endif
+  }
+
   // Methods to control playback of the stream.
 
   // Starts the playback of this audio output stream.
   void Play();
 
   // Pause this audio output stream.
   void Pause();
 
   // Closes the audio output stream. The state is changed and the resources
   // are freed on the audio manager thread. closed_task is executed after that.
@@ skipping 48 matching lines @@
   // Internal state of the source.
   enum State {
     kEmpty,
     kCreated,
     kPlaying,
     kPaused,
     kClosed,
     kError,
   };
 
+  // Time constant for AudioPowerMonitor.  See AudioPowerMonitor ctor comments
+  // for semantics.  This value was arbitrarily chosen, but seems to work well.
+  enum { kPowerMeasurementTimeConstantMillis = 10 };
+
   friend class base::RefCountedThreadSafe<AudioOutputController>;
   virtual ~AudioOutputController();
 
  private:
   AudioOutputController(AudioManager* audio_manager, EventHandler* handler,
                         const AudioParameters& params,
                         const std::string& output_device_id,
                         SyncReader* sync_reader);
 
   // The following methods are executed on the audio manager thread.
@@ skipping 37 matching lines @@
   // hardware audio thread. These operations need to be locked. But lock
   // is not required for reading on the audio manager thread.
   State state_;
 
   // SyncReader is used only in low latency mode for synchronous reading.
   SyncReader* const sync_reader_;
 
   // The message loop of audio manager thread that this object runs on.
   const scoped_refptr<base::SingleThreadTaskRunner> message_loop_;
 
-#if defined(AUDIO_POWER_MONITORING)
   // Scans audio samples from OnMoreData() as input to compute power levels.
   AudioPowerMonitor power_monitor_;
-#endif
 
   // Flags when we've asked for a stream to start but it never did.
   base::AtomicRefCount on_more_io_data_called_;
   scoped_ptr<base::OneShotTimer<AudioOutputController> > wedge_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputController);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_