Reland of "Adds a WebRTC browser_test with opus dtx enabled.".

chrome/test/data/webrtc/peerconnection.js

 /**
  * Copyright 2014 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.
  */
 
 /**
  * The one and only peer connection in this page.
  * @private
  */
 var gPeerConnection = null;
 
 /**
  * This stores ICE candidates generated on this side.
  * @private
  */
 var gIceCandidates = [];
 
 /**
  * Keeps track of whether we have seen crypto information in the SDP.
  * @private
  */
 var gHasSeenCryptoInSdp = 'no-crypto-seen';
 
+/**
+ * The default video codec that should be used.
+ * @private
+ */
+var gDefaultVideoCodec = null;
+
+/**
+ * Flag to indicate if Opus Dtx should be enabled.
+ * @private
+ */
+var gOpusDtx = false;
+
 // Public interface to tests. These are expected to be called with
 // ExecuteJavascript invocations from the browser tests and will return answers
 // through the DOM automation controller.
 
 /**
  * Creates a peer connection. Must be called before most other public functions
  * in this file. Alternatively, see |preparePeerConnectionWithCertificate|.
  * @param {Object} keygenAlgorithm Unless null, this is an |AlgorithmIdentifier|
  * to be used as parameter to |RTCPeerConnection.generateCertificate|. The
  * resulting certificate will be used by the peer connection. If null, a default
@@ skipping 26 matching lines @@
  */
 function preparePeerConnectionWithCertificate(certificate) {
   if (gPeerConnection !== null)
     throw failTest('Creating peer connection, but we already have one.');
   gPeerConnection = createPeerConnection_(
       {iceServers:[], certificates:[certificate]});
   returnToTest('ok-peerconnection-created');
 }
 
 /**
+ * Sets the flag to force Opus Dtx to be used when creating an offer.
+ */
+function forceOpusDtx() {
+  gOpusDtx = true;
+  returnToTest('ok-forced');
+}
+
+/**
+ * Sets the default video codec be used when creating an offer.
+ * @param {string} videoCodec promotes the specified codec to be the default
+ *     video codec, e.g. the first one in the list on the 'm=video' SDP offer
+ *     line. |videoCodec| is the case-sensitive codec name, e.g. 'VP8' or
+ *     'H264'.
+ */
+function forceVideoCodec(videoCodec) {
+  gDefaultVideoCodec = videoCodec;
+  returnToTest('ok-forced');
+}
+
+/**
  * Asks this page to create a local offer.
  *
  * Returns a string on the format ok-(JSON encoded session description).
  *
  * @param {!Object} constraints Any createOffer constraints.
- * @param {string} videoCodec If not null, promotes the specified codec to be
- *     the default video codec, e.g. the first one in the list on the 'm=video'
- *     SDP offer line. |videoCodec| is the case-sensitive codec name, e.g.
- *     'VP8' or 'H264'.
  */
-function createLocalOffer(constraints, videoCodec = null) {
+function createLocalOffer(constraints) {
   peerConnection_().createOffer(
       function(localOffer) {
         success('createOffer');
 
         setLocalDescription(peerConnection, localOffer);
-        if (videoCodec !== null)
-          localOffer.sdp = setSdpDefaultVideoCodec(localOffer.sdp, videoCodec);
-
+        if (gDefaultVideoCodec !== null) {
+          localOffer.sdp = setSdpDefaultVideoCodec(localOffer.sdp,
+                                                   gDefaultVideoCodec);
+        }
+        if (gOpusDtx) {
+          localOffer.sdp = setOpusDtxEnabled(localOffer.sdp);
+        }
         returnToTest('ok-' + JSON.stringify(localOffer));
       },
       function(error) { failure('createOffer', error); },
       constraints);
 }
 
 /**
  * Asks this page to accept an offer and generate an answer.
  *
  * Returns a string on the format ok-(JSON encoded session description).
@@ skipping 12 matching lines @@
   var sessionDescription = new RTCSessionDescription(offer);
   peerConnection_().setRemoteDescription(
       sessionDescription,
       function() { success('setRemoteDescription'); },
       function(error) { failure('setRemoteDescription', error); });
 
   peerConnection_().createAnswer(
       function(answer) {
         success('createAnswer');
         setLocalDescription(peerConnection, answer);
+        if (gOpusDtx) {
+          answer.sdp = setOpusDtxEnabled(answer.sdp);
+        }
         returnToTest('ok-' + JSON.stringify(answer));
       },
       function(error) { failure('createAnswer', error); },
       constraints);
 }
 
 /**
- * Verifies that the specified codec is the default video codec, e.g. the first
- * one in the list on the 'm=video' SDP answer line. If this is not the case,
- * |failure| occurs.
+ * Verifies that the codec previously set using forceVideoCodec() is the
+ * default video codec, e.g. the first one in the list on the 'm=video' SDP
+ * answer line. If this is not the case, |failure| occurs. If no codec was
+ * previously set using forceVideoCodec(), this function will return
+ * 'ok-no-default-set'.
  *
  * @param {!string} sessionDescJson A JSON-encoded session description.
- * @param {!string} expectedVideoCodec The case-sensitive codec name, e.g.
- *     'VP8' or 'H264'.
  */
-function verifyDefaultVideoCodec(sessionDescJson, expectedVideoCodec) {
+function verifyDefaultVideoCodec(sessionDescJson) {
   var sessionDesc = parseJson_(sessionDescJson);
+  if (gDefaultVideoCodec === null) {
+    returnToTest('ok-no-default-set');
+    return;
+  }
   if (!sessionDesc.type) {
     failure('verifyDefaultVideoCodec',
              'Invalid session description: ' + sessionDescJson);
   }
   var defaultVideoCodec = getSdpDefaultVideoCodec(sessionDesc.sdp);
   if (defaultVideoCodec === null) {
     failure('verifyDefaultVideoCodec',
              'Could not determine default video codec.');
   }
-  if (expectedVideoCodec !== defaultVideoCodec) {
+  if (gDefaultVideoCodec !== defaultVideoCodec) {
     failure('verifyDefaultVideoCodec',
-             'Expected default video codec ' + expectedVideoCodec +
+             'Expected default video codec ' + gDefaultVideoCodec +
              ', got ' + defaultVideoCodec + '.');
   }
   returnToTest('ok-verified');
 }
 
 /**
  * Asks this page to accept an answer generated by the peer in response to a
  * previous offer by this page
  *
  * Returns a string ok-accepted-answer on success.
@@ skipping 213 matching lines @@
 function parseJson_(json) {
   // Escape since the \r\n in the SDP tend to get unescaped.
   jsonWithEscapedLineBreaks = json.replace(/\r\n/g, '\\r\\n');
   try {
     return JSON.parse(jsonWithEscapedLineBreaks);
   } catch (exception) {
     failTest('Failed to parse JSON: ' + jsonWithEscapedLineBreaks + ', got ' +
              exception);
   }
 }