Made sure empty-call-then-add-one-stream test doesn't do simultaneous negotiations.

content/test/data/media/webrtc_test_utilities.js

 // Copyright (c) 2012 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.
 
 // These must match with how the video and canvas tags are declared in html.
 const VIDEO_TAG_WIDTH = 320;
 const VIDEO_TAG_HEIGHT = 240;
 
 // Number of test events to occur before the test pass. When the test pass,
 // the function gAllEventsOccured is called.
@@ skipping 26 matching lines @@
     }
   }, 100);
 }
 
 function waitForVideo(videoElement) {
   document.title = 'Waiting for video...';
   addExpectedEvent();
   detectVideoIn(videoElement, function () { eventOccured(); });
 }
 
+function waitForConnectionToStabilize(peerConnection) {
+  addExpectedEvent();
+  var waitForStabilization = setInterval(function() {
+    if (peerConnection.signalingState == 'stable') {
+      clearInterval(waitForStabilization);
+      eventOccured();
+    }
+  }, 100);
+}
+
 function addExpectedEvent() {
   ++gNumberOfExpectedEvents;
 }
 
 function eventOccured() {
   ++gNumberOfEvents;
   if (gNumberOfEvents == gNumberOfExpectedEvents) {
     gAllEventsOccured();
   }
 }
@@ skipping 14 matching lines @@
 
 // This function matches |left| and |right| and throws an exception if the
 // values don't match.
 function expectEquals(left, right) {
   if (left != right) {
     var s = "expectEquals failed left: " + left + " right: " + right;
     document.title = s;
     throw s;
   }
 }