diff --git a/dom/media/tests/mochitest/identity/test_fingerprints.html b/dom/media/tests/mochitest/identity/test_fingerprints.html
index 0fd065af26d9..bf26c2fdd5e6 100644
--- a/dom/media/tests/mochitest/identity/test_fingerprints.html
+++ b/dom/media/tests/mochitest/identity/test_fingerprints.html
@@ -86,8 +86,7 @@ function testMultipleFingerprints() {
           fingerprintSdp(fingerprints.slice(1)) +
           offer.sdp.slice(match.index);
 
-      var desc = new RTCSessionDescription({ type: 'offer', sdp: sdp });
-      return pcStrict.setRemoteDescription(desc);
+      return pcStrict.setRemoteDescription({ type: 'offer', sdp });
     })
     .then(() => {
       ok(true, 'Modified fingerprints were accepted');
diff --git a/dom/media/tests/mochitest/pc.js b/dom/media/tests/mochitest/pc.js
index 37e3b7e36f44..446152842a5a 100644
--- a/dom/media/tests/mochitest/pc.js
+++ b/dom/media/tests/mochitest/pc.js
@@ -334,7 +334,7 @@ PeerConnectionTest.prototype.createOffer = function(peer) {
  *
  * @param {PeerConnectionWrapper} peer
           The peer connection wrapper to run the command on
- * @param {RTCSessionDescription} desc
+ * @param {RTCSessionDescriptionInit} desc
  *        Session description for the local description request
  */
 PeerConnectionTest.prototype.setLocalDescription =
@@ -403,7 +403,7 @@ PeerConnectionTest.prototype.setOfferOptions = function(options) {
  *
  * @param {PeerConnectionWrapper} peer
           The peer connection wrapper to run the command on
- * @param {RTCSessionDescription} desc
+ * @param {RTCSessionDescriptionInit} desc
  *        Session description for the remote description request
  */
 PeerConnectionTest.prototype.setRemoteDescription =
@@ -1071,7 +1071,7 @@ PeerConnectionWrapper.prototype = {
    * Sets the local description and automatically handles the failure case.
    *
    * @param {object} desc
-   *        RTCSessionDescription for the local description request
+   *        RTCSessionDescriptionInit for the local description request
    */
   setLocalDescription : function(desc) {
     this.observedNegotiationNeeded = undefined;
@@ -1085,7 +1085,7 @@ PeerConnectionWrapper.prototype = {
    * causes the test case to fail if the call succeeds.
    *
    * @param {object} desc
-   *        RTCSessionDescription for the local description request
+   *        RTCSessionDescriptionInit for the local description request
    * @returns {Promise}
    *        A promise that resolves to the expected error
    */
@@ -1102,7 +1102,7 @@ PeerConnectionWrapper.prototype = {
    * Sets the remote description and automatically handles the failure case.
    *
    * @param {object} desc
-   *        RTCSessionDescription for the remote description request
+   *        RTCSessionDescriptionInit for the remote description request
    */
   setRemoteDescription : function(desc) {
     this.observedNegotiationNeeded = undefined;
@@ -1122,7 +1122,7 @@ PeerConnectionWrapper.prototype = {
    * causes the test case to fail if the call succeeds.
    *
    * @param {object} desc
-   *        RTCSessionDescription for the remote description request
+   *        RTCSessionDescriptionInit for the remote description request
    * @returns {Promise}
    *        a promise that resolve to the returned error
    */
diff --git a/dom/media/tests/mochitest/test_peerConnection_errorCallbacks.html b/dom/media/tests/mochitest/test_peerConnection_errorCallbacks.html
index 6d152a4fa6b5..9ae3b8d50f86 100644
--- a/dom/media/tests/mochitest/test_peerConnection_errorCallbacks.html
+++ b/dom/media/tests/mochitest/test_peerConnection_errorCallbacks.html
@@ -27,8 +27,7 @@
   function testSetLocalDescriptionError() {
     var pc = new RTCPeerConnection();
     info ("Testing setLocalDescription error");
-    return pc.setLocalDescription(new RTCSessionDescription({ sdp: "Picklechips!",
-                                                                 type: "offer" }))
+    return pc.setLocalDescription({ sdp: "Picklechips!", type: "offer" })
     .then(generateErrorCallback("setLocalDescription with nonsense SDP should fail"),
           validateReason);
   };
@@ -36,8 +35,7 @@
   function testSetRemoteDescriptionError() {
     var pc = new RTCPeerConnection();
     info ("Testing setRemoteDescription error");
-    return pc.setRemoteDescription(new RTCSessionDescription({ sdp: "Who?",
-                                                                  type: "offer" }))
+    return pc.setRemoteDescription({ sdp: "Who?", type: "offer" })
     .then(generateErrorCallback("setRemoteDescription with nonsense SDP should fail"),
           validateReason);
   };
diff --git a/dom/media/tests/mochitest/test_peerConnection_localReofferRollback.html b/dom/media/tests/mochitest/test_peerConnection_localReofferRollback.html
index 0b0b35fe80b6..ed149747cab5 100644
--- a/dom/media/tests/mochitest/test_peerConnection_localReofferRollback.html
+++ b/dom/media/tests/mochitest/test_peerConnection_localReofferRollback.html
@@ -37,10 +37,9 @@
         },
 
         function PC_REMOTE_ROLLBACK(test) {
-          return test.setLocalDescription(
-              test.pcRemote,
-              new RTCSessionDescription({ type: "rollback", sdp: ""}),
-              STABLE);
+          return test.setLocalDescription(test.pcRemote,
+                                          { type: "rollback", sdp: "" },
+                                          STABLE);
         },
 
         // Rolling back should shut down gathering
diff --git a/dom/media/tests/mochitest/test_peerConnection_localRollback.html b/dom/media/tests/mochitest/test_peerConnection_localRollback.html
index 2a35920baa6d..45ceba844e6f 100644
--- a/dom/media/tests/mochitest/test_peerConnection_localRollback.html
+++ b/dom/media/tests/mochitest/test_peerConnection_localRollback.html
@@ -23,10 +23,9 @@
         },
 
         function PC_REMOTE_ROLLBACK(test) {
-          return test.setLocalDescription(
-              test.pcRemote,
-              new RTCSessionDescription({ type: "rollback", sdp: ""}),
-              STABLE);
+          return test.setLocalDescription(test.pcRemote,
+                                          { type: "rollback", sdp: "" },
+                                          STABLE);
         },
 
         // Rolling back should shut down gathering
diff --git a/dom/media/tests/mochitest/test_peerConnection_remoteReofferRollback.html b/dom/media/tests/mochitest/test_peerConnection_remoteReofferRollback.html
index 6b518e1d29d6..7580358b86b7 100644
--- a/dom/media/tests/mochitest/test_peerConnection_remoteReofferRollback.html
+++ b/dom/media/tests/mochitest/test_peerConnection_remoteReofferRollback.html
@@ -35,10 +35,8 @@
         },
 
         function PC_REMOTE_ROLLBACK(test) {
-          return test.setRemoteDescription(
-              test.pcRemote,
-              new RTCSessionDescription({ type: "rollback" }),
-              STABLE)
+          return test.setRemoteDescription(test.pcRemote, { type: "rollback" },
+                                           STABLE)
             .then(() => test.pcRemote.rollbackRemoteTracksIfNotNegotiated());
         },
 
diff --git a/dom/media/tests/mochitest/test_peerConnection_remoteRollback.html b/dom/media/tests/mochitest/test_peerConnection_remoteRollback.html
index 099628ab88a3..35a51d03c098 100644
--- a/dom/media/tests/mochitest/test_peerConnection_remoteRollback.html
+++ b/dom/media/tests/mochitest/test_peerConnection_remoteRollback.html
@@ -20,10 +20,8 @@
       function PC_REMOTE_ROLLBACK(test) {
         // We still haven't negotiated the tracks
         test.pcRemote.expectNegotiationNeeded();
-        return test.setRemoteDescription(
-          test.pcRemote,
-          new RTCSessionDescription({ type: "rollback" }),
-          STABLE)
+        return test.setRemoteDescription(test.pcRemote, { type: "rollback" },
+                                         STABLE)
           .then(() => test.pcRemote.rollbackRemoteTracksIfNotNegotiated());
       },
 
diff --git a/dom/media/tests/mochitest/test_peerConnection_restartIceLocalAndRemoteRollback.html b/dom/media/tests/mochitest/test_peerConnection_restartIceLocalAndRemoteRollback.html
index e92617164478..d2280cee87be 100644
--- a/dom/media/tests/mochitest/test_peerConnection_restartIceLocalAndRemoteRollback.html
+++ b/dom/media/tests/mochitest/test_peerConnection_restartIceLocalAndRemoteRollback.html
@@ -51,10 +51,8 @@
         },
 
         function PC_REMOTE_ROLLBACK(test) {
-          return test.setRemoteDescription(
-              test.pcRemote,
-              new RTCSessionDescription({ type: "rollback" }),
-              STABLE);
+          return test.setRemoteDescription(test.pcRemote, { type: "rollback" },
+                                           STABLE);
         },
 
         function PC_LOCAL_ROLLBACK(test) {
diff --git a/dom/media/tests/mochitest/test_peerConnection_restartIceLocalRollback.html b/dom/media/tests/mochitest/test_peerConnection_restartIceLocalRollback.html
index c1ac186de1a4..fd9fee9c0c56 100644
--- a/dom/media/tests/mochitest/test_peerConnection_restartIceLocalRollback.html
+++ b/dom/media/tests/mochitest/test_peerConnection_restartIceLocalRollback.html
@@ -42,11 +42,9 @@
           test.pcLocal.iceCheckingIceRollbackExpected = true;
         },
         function PC_LOCAL_ROLLBACK(test) {
-          return test.setLocalDescription(
-              test.pcLocal,
-              new RTCSessionDescription({ type: "rollback",
-                                          sdp: ""}),
-              STABLE);
+          return test.setLocalDescription(test.pcLocal,
+                                          { type: "rollback", sdp: ""},
+                                          STABLE);
         },
         // Rolling back should shut down gathering
         function PC_LOCAL_WAIT_FOR_END_OF_TRICKLE(test) {