Implementation of 'AudioContext.getOutputTimestamp' method

media/audio/audio_io.h

Index: media/audio/audio_io.h
diff --git a/media/audio/audio_io.h b/media/audio/audio_io.h
index 66ff3f2dc98cf7af2324fa1cb58944e29c003342..bac385e0f25935d35c0defd64123ec67ba26b5e5 100644
--- a/media/audio/audio_io.h
+++ b/media/audio/audio_io.h
@@ -49,6 +49,16 @@
 
 namespace media {
 
+struct MEDIA_EXPORT AudioTimestamp {
+  int64_t frames;
+  int64_t ticks;  // Obtained from base::TimeTicks::ToInternalValue().
+};
+
+// Used in unittests.
+inline bool operator==(const AudioTimestamp& one, const AudioTimestamp& other) {
+  return one.ticks == other.ticks && one.frames == other.frames;
+}
+
 class MEDIA_EXPORT AudioOutputStream {
  public:
   // Audio sources must implement AudioSourceCallback. This interface will be
@@ -63,9 +73,12 @@ class MEDIA_EXPORT AudioOutputStream {
     // the number of frames it filled.  |total_bytes_delay| contains current
     // number of bytes of delay buffered by the AudioOutputStream.
     // |frames_skipped| contains the number of frames skipped by the consumer.
+    // |timestamp| if provided, contains timestamp of the currently audible
+    // signal.
     virtual int OnMoreData(AudioBus* dest,
                            uint32_t total_bytes_delay,
-                           uint32_t frames_skipped) = 0;
+                           uint32_t frames_skipped,
+                           const AudioTimestamp& output_timestamp = {0, 0}) = 0;
 
     // There was an error while playing a buffer. Audio source cannot be
     // destroyed yet. No direct action needed by the AudioStream, but it is