Add support creating and saving a new reference file.

third_party/WebKit/LayoutTests/webaudio/resources/audit-util.js

 // Copyright 2016 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.
 
 
 /**
  * @fileOverview  This file includes legacy utility functions for the layout
  *                test.
  */
 
@@ skipping 91 matching lines @@
 function createAudioData(audioBuffer) {
     return createWaveFileData(audioBuffer);
 }
 
 function finishAudioTest(event) {
     var audioData = createAudioData(event.renderedBuffer);
     testRunner.setAudioData(audioData);
     testRunner.notifyDone();
 }
 
+// Save the given |audioBuffer| to a 16-bit WAV file using the name
+// given by |filename|.  This is intended to be run from a browser.
+// The developer is expected to use the console to run
+// downloadAudioBuffer when necessary to create a new reference file
+// for a test.
+function downloadAudioBuffer(audioBuffer, filename) {
+    // Don't download if testRunner is defined; we're running a layout
+    // test where this won't be useful in general.
+    if (window.testRunner)
+        return false;
+    // Convert the audio buffer to an array containing the WAV file
+    // contents.  Then convert it to a blob that can be saved as a WAV
+    // file.
+    let wavData = createAudioData(audioBuffer);
+    let blob = new Blob([wavData], {type: 'audio/wav'});
+    // Manually create html tags for downloading, and simulate a click
+    // to download the file to the given file name.
+    let a = document.createElement('a');
+    a.style.display = 'none';
+    a.download = filename;
+    let audioURL = window.URL.createObjectURL(blob);
+    let audio = new Audio();
+    audio.src = audioURL;
+    a.href = audioURL;
+    document.body.appendChild(a);
+    a.click();
+    return true;
+}
+
 // Compare two arrays (commonly extracted from buffer.getChannelData()) with
 // constraints:
 //   options.thresholdSNR: Minimum allowed SNR between the actual and expected
 //     signal. The default value is 10000.
 //   options.thresholdDiffULP: Maximum allowed difference between the actual
 //     and expected signal in ULP(Unit in the last place). The default is 0.
 //   options.thresholdDiffCount: Maximum allowed number of sample differences
 //     which exceeds the threshold. The default is 0.
 //   options.bitDepth: The expected result is assumed to come from an audio
 //     file with this number of bits of precision. The default is 16.
@@ skipping 146 matching lines @@
     var length = Math.min(actual.length, expected.length);
 
     for (var k = 0; k < length; ++k) {
         var diff = actual[k] - expected[k];
         signalPower += expected[k] * expected[k];
         noisePower += diff * diff;
     }
 
     return signalPower / noisePower;
 }