Adds a WebRTC browser_test with opus dtx enabled.

chrome/test/data/webrtc/peerconnection.js

Index: chrome/test/data/webrtc/peerconnection.js
diff --git a/chrome/test/data/webrtc/peerconnection.js b/chrome/test/data/webrtc/peerconnection.js
index 639e0f41a8ff34624bc5be8ea6fed1aeb640b757..ec9ea0bffcd71aaeda52a4499fa318b87fe59702 100644
--- a/chrome/test/data/webrtc/peerconnection.js
+++ b/chrome/test/data/webrtc/peerconnection.js
@@ -22,6 +22,18 @@ var gIceCandidates = [];
  */
 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.
@@ -68,25 +80,45 @@ function preparePeerConnectionWithCertificate(certificate) {
 }
 
 /**
+ * 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); },
@@ -117,8 +149,14 @@ function receiveOfferFromPeer(sessionDescJson, constraints) {
 
   peerConnection_().createAnswer(
       function(answer) {
+        if (gDefaultVideoCodec !== null) {
+          verifyDefaultVideoCodec(answer.sdp, gDefaultVideoCodec);

[phoglund_chromium, 2016/07/28 06:39:01]

I still want to keep the verification as a separate test call in order to keep
this function simple. What happened to dtx verification by the way?

[Ivo-OOO until feb 6, 2016/07/28 12:29:31]

Ok, done. 
I realized that dtx verification is a bit useless, since we're actually setting
it manually in the setOpusDtxEnabled function below (which will generate a
failure if it runs into problems). So it was basically verifying the work done
by setOpusDtxEnabled, which doesn't seem terribly useful to me.

+        }
         success('createAnswer');
         setLocalDescription(peerConnection, answer);
+        if (gOpusDtx) {
+          answer.sdp = setOpusDtxEnabled(answer.sdp);
+        }
         returnToTest('ok-' + JSON.stringify(answer));
       },
       function(error) { failure('createAnswer', error); },
@@ -134,13 +172,8 @@ function receiveOfferFromPeer(sessionDescJson, constraints) {
  * @param {!string} expectedVideoCodec The case-sensitive codec name, e.g.
  *     'VP8' or 'H264'.
  */
-function verifyDefaultVideoCodec(sessionDescJson, expectedVideoCodec) {
-  var sessionDesc = parseJson_(sessionDescJson);
-  if (!sessionDesc.type) {
-    failure('verifyDefaultVideoCodec',
-             'Invalid session description: ' + sessionDescJson);
-  }
-  var defaultVideoCodec = getSdpDefaultVideoCodec(sessionDesc.sdp);
+function verifyDefaultVideoCodec(sdp, expectedVideoCodec) {
+  var defaultVideoCodec = getSdpDefaultVideoCodec(sdp);
   if (defaultVideoCodec === null) {
     failure('verifyDefaultVideoCodec',
              'Could not determine default video codec.');
@@ -150,7 +183,6 @@ function verifyDefaultVideoCodec(sessionDescJson, expectedVideoCodec) {
              'Expected default video codec ' + expectedVideoCodec +
              ', got ' + defaultVideoCodec + '.');
   }
-  returnToTest('ok-verified');
 }
 
 /**