Implement AudioRendererMixerInput::CurrentThreadIsRenderingThread().

media/base/audio_renderer_mixer_input.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.
 //
 // THREAD SAFETY
 //
 // This class is generally not thread safe. Callers should ensure thread safety.
 // For instance, the |sink_lock_| in WebAudioSourceProvider synchronizes access
 // to this object across the main thread (for WebAudio APIs) and the
 // media thread (for HTMLMediaElement APIs).
@@ skipping 33 matching lines @@
   void Stop() override;
   void Play() override;
   void Pause() override;
   bool SetVolume(double volume) override;
   OutputDeviceInfo GetOutputDeviceInfo() override;
   void Initialize(const AudioParameters& params,
                   AudioRendererSink::RenderCallback* renderer) override;
   void SwitchOutputDevice(const std::string& device_id,
                           const url::Origin& security_origin,
                           const OutputDeviceStatusCB& callback) override;
+  // This is expected to be called on the audio rendering thread. The caller
+  // must ensure that this input has been added to a mixer before calling the
+  // function, and that it is not removed from the mixer before this function
+  // returns.
   bool CurrentThreadIsRenderingThread() override;
 
   // Called by AudioRendererMixer when an error occurs.
   void OnRenderError();
 
  protected:
   ~AudioRendererMixerInput() override;
 
  private:
   friend class AudioRendererMixerInputTest;
@@ skipping 34 matching lines @@
   OutputDeviceStatusCB pending_switch_callback_;
   std::string pending_switch_device_id_;
   url::Origin pending_switch_security_origin_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioRendererMixerInput);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_RENDERER_MIXER_INPUT_H_