WebRTC: Use the MediaStream Recording API for the audio_quality_browsertest.

chrome/test/data/webrtc/audio_extraction.js

Index: chrome/test/data/webrtc/audio_extraction.js
diff --git a/chrome/test/data/webrtc/audio_extraction.js b/chrome/test/data/webrtc/audio_extraction.js
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+/**
+ * Copyright (c) 2017 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.
+ */
+
+/**
+ * Aggregate target bits per second for encoding of the Audio track.
+ * @private
+ */
+var gAudioBitsPerSecond = 3000000;
+
+/**
+ * The duration of the audio recording in milliseconds.
+ * @private
+ */
+var gCaptureDuration = 0;
+
+/**
+ * The recorded audio encoded in Base64.
+ * @private
+ */
+var gAudioBase64 = '';
+
+/**
+ * Chunks of the audio recorded by MediaRecorded as they become available.
+ * @private
+ */
+var gChunks = [];
+
+/**
+ * A string to be returned to the test about the current status of capture.
+ */
+var gCapturingStatus = 'capturing-not-started';
+
+/**
+ * Starts the audio capturing.
+ *
+ * @param {Number} The duration of the capture in seconds.
+ */
+function startAudioCapture(duration) {
+  console.log('started-capture');
+  var inputElement = document.getElementById('remote-view');
+
+  // |audioBitsPerSecond| must set to a large number to throw as little
+  // information away as possible.
+  var mediaRecorderOptions = {
+    audioBitsPerSecond: gAudioBitsPerSecond,
+    mimeType: 'audio/webm',
+  };
+  var stream = getStreamFromElement_(inputElement);
+  gCaptureDuration = 1000 * duration;
+
+  var mediaRecorder = new MediaRecorder(stream, mediaRecorderOptions);
+
+  mediaRecorder.ondataavailable = function(recording) {
+    gChunks.push(recording.data);
+  }
+  mediaRecorder.onstop = function() {
+    console.log(gChunks.length);
+    var audioBlob = new Blob(gChunks, {type: "audio/webm"});
+    gChunks = [];
+    var reader = new FileReader();
+    reader.onloadend = function() {
+      gAudioBase64 = reader.result.substr(reader.result.indexOf(',') + 1);
+      gCapturingStatus = 'done-capturing';
+      debug('done-capturing');
+    }
+    reader.readAsDataURL(audioBlob);
+  }
+
+  mediaRecorder.start();
+  setTimeout(function() { mediaRecorder.stop(); }, gCaptureDuration);
+  gCapturingStatus = 'still-capturing';
+}
+
+/**
+ * Returns the audio recorded by RecordMedia encoded in Base64.
+ */
+function getRecordedAudioAsBase64() {
+  silentReturnToTest(gAudioBase64);
+}
+
+/**
+ * Queries if we're done with the capturing yet.
+ */
+function doneCapturingAudio() {
+  returnToTest(gCapturingStatus);
+}
+
+/**
+ * Returns the stream from the input element to be attached to MediaRecorder.
+ * @private
+ */
+function getStreamFromElement_(element) {
+  if (element.srcObject !== undefined) {
+    return element.srcObject;
+  } else if (element.src !== undefined) {
+    return element.src;
+  } else {
+    failTest('Error extracting stream from element.');
+  }
+}