Hookup the MediaStream glue for Adding and Removing tracks to an existing MediaStream.

content/test/data/media/webrtc_test_utilities.js

+// 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.
+var gNumberOfExpectedEvents = 0;
+
+// Number of events that currently have occurred.
+var gNumberOfEvents = 0;
+

[phoglund_chromium, 2013/04/11 11:16:48]

Write a small accessor to overwrite this guy which is then called by the two
other files. I think we should avoid overwriting globals in other files
directly.

[perkj_chrome, 2013/04/11 11:50:48]

Done.

+var gAllEventsOccured = function () {};
+
+function detectVideoIn(videoElementName, callback) {
+  var width = VIDEO_TAG_WIDTH;
+  var height = VIDEO_TAG_HEIGHT;
+  var videoElement = $(videoElementName);
+  var canvas = $(videoElementName + '-canvas');
+  var waitVideo = setInterval(function() {
+    var context = canvas.getContext('2d');
+    context.drawImage(videoElement, 0, 0, width, height);
+    var pixels = context.getImageData(0, 0, width, height).data;
+
+    if (isVideoPlaying(pixels, width, height)) {
+      clearInterval(waitVideo);
+      callback();
+    }
+  }, 100);
+}
+
+function waitForVideo(videoElement) {
+  document.title = 'Waiting for video...';
+  addExpectedEvent();
+  detectVideoIn(videoElement, function () { eventOccured(); });
+}
+
+function addExpectedEvent() {
+  ++gNumberOfExpectedEvents;
+}
+
+function eventOccured() {
+  ++gNumberOfEvents;
+  if (gNumberOfEvents == gNumberOfExpectedEvents) {
+    gAllEventsOccured();
+  }
+}
+
+// This very basic video verification algorithm will be satisfied if any
+// pixels are nonzero in a small sample area in the middle. It relies on the
+// assumption that a video element with null source just presents zeroes.
+function isVideoPlaying(pixels, width, height) {
+  // Sample somewhere near the middle of the image.
+  var middle = width * height / 2;
+  for (var i = 0; i < 20; i++) {
+    if (pixels[middle + i] > 0) {
+      return true;
+    }
+  }
+  return false;
+}
+
+// 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;
+  }
+}