Add detection for repeated audio in capturing.

content/renderer/media/media_stream_audio_processor.cc

Index: content/renderer/media/media_stream_audio_processor.cc
diff --git a/content/renderer/media/media_stream_audio_processor.cc b/content/renderer/media/media_stream_audio_processor.cc
index 56d9570720d5eb9f97005203956ca652b0b010be..a2f08920089005e427032ca9f44a66e58cf8d0a1 100644
--- a/content/renderer/media/media_stream_audio_processor.cc
+++ b/content/renderer/media/media_stream_audio_processor.cc
@@ -239,6 +239,7 @@ MediaStreamAudioProcessor::MediaStreamAudioProcessor(
     const MediaStreamDevice::AudioDeviceParameters& input_params,
     WebRtcPlayoutDataSource* playout_data_source)
     : render_delay_ms_(0),
+      audio_repetition_detector_(new AudioRepetitionDetector()),
       playout_data_source_(playout_data_source),
       audio_mirroring_(false),
       typing_detected_(false),
@@ -298,6 +299,15 @@ bool MediaStreamAudioProcessor::ProcessAndConsumeData(
   if (!capture_fifo_->Consume(&process_bus, capture_delay))
     return false;
 
+  // Detect bit-exact repetition of audio present in the captured audio.
+  // We detect only one channel.
+  if (audio_repetition_detector_) {

[ajm, 2015/09/30 00:23:43]

Why do you need to check this?

[minyue, 2015/09/30 19:52:32]

Good point. Tommi asked about whether audio_repetition_detector_ needed to be
always created, I answered it, but should have realized that this check could be
removed.

+    audio_repetition_detector_->Detect(process_bus->bus()->channel(0),
+                                       process_bus->bus()->frames(),
+                                       1,  // number of channels
+                                       input_format_.sample_rate());
+  }
+
   // Use the process bus directly if audio processing is disabled.
   MediaStreamAudioBus* output_bus = process_bus;
   *new_volume = 0;