Implementation of 'AudioContext.getOutputTimestamp' method

media/audio/win/audio_low_latency_output_win.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.
 
 // Implementation of AudioOutputStream for Windows using Windows Core Audio
 // WASAPI for low latency rendering.
 //
 // Overview of operation and performance:
 //
 // - An object of WASAPIAudioOutputStream is created by the AudioManager
@@ skipping 221 matching lines @@
   // data to a rendering endpoint buffer.
   base::win::ScopedComPtr<IAudioRenderClient> audio_render_client_;
 
   // The audio engine will signal this event each time a buffer becomes
   // ready to be filled by the client.
   base::win::ScopedHandle audio_samples_render_event_;
 
   // This event will be signaled when rendering shall stop.
   base::win::ScopedHandle stop_render_event_;
 
+  // A ratio used to convert 100-nanosecond 'pu64QPCPosition' time units
+  // (obtained from IAudioClock::GetPosition()) to raw performance counter
+  // time units.
+  double hns_units_to_perf_count_;
+
   // Container for retrieving data from AudioSourceCallback::OnMoreData().
   std::unique_ptr<AudioBus> audio_bus_;
 
   base::win::ScopedComPtr<IAudioClock> audio_clock_;
 
   DISALLOW_COPY_AND_ASSIGN(WASAPIAudioOutputStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_WIN_AUDIO_LOW_LATENCY_OUTPUT_WIN_H_