Add simple test for VideoTrack.stop().

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;
 
 // Fake video capture background green is of value 135.
 const COLOR_BACKGROUND_GREEN = 135;
 
 // 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;
 
 var gAllEventsOccured = function () {};
 
 // Use this function to set a function that will be called once all expected
 // events has occurred.
 function setAllEventsOccuredHandler(handler) {
   gAllEventsOccured = handler;
 }
 
-function detectVideoIn(videoElementName, callback) {
+function detectVideoPlaying(videoElementName, callback) {
+  detectVideo(videoElementName, isVideoPlaying, callback);
+}
+
+function detectVideoStopped(videoElementName, callback) {
+  detectVideo(videoElementName,
+              function (pixels, previous_pixels) {
+                return !isVideoPlaying(pixels, previous_pixels);
+              },
+              callback);
+}
+
+function detectVideo(videoElementName, predicate, callback) {
   var width = VIDEO_TAG_WIDTH;
   var height = VIDEO_TAG_HEIGHT;
   var videoElement = $(videoElementName);
   var canvas = $(videoElementName + '-canvas');
+  var old_pixels = [];
   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)) {
+    var pixels = context.getImageData(0, 0 , width, height / 3).data;
+    // Check that there is an old and a new picture with the same size to
+    // compare and use the function |predicate| to detect the video state in
+    // that case.
+    if (old_pixels.length == pixels.length &&
+        predicate(pixels, old_pixels)) {
       clearInterval(waitVideo);
       callback();
     }
-  }, 100);
+    old_pixels = pixels;
+  }, 200);
 }
 
 function waitForVideo(videoElement) {
   document.title = 'Waiting for video...';
   addExpectedEvent();
-  detectVideoIn(videoElement, function () { eventOccured(); });
+  detectVideoPlaying(videoElement, function () { eventOccured(); });
+}
+
+function waitForVideoToStop(videoElement) {
+  document.title = 'Waiting for video to stop...';
+  addExpectedEvent();
+  detectVideoStopped(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();
   }
 }
 
 // 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) {
+// pixels are changed.
+function isVideoPlaying(pixels, previous_pixels) {
+  for (var i = 0; i < pixels.length; i++) {
+    if (pixels[i] != previous_pixels[i]) {
       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) {
@@ skipping 82 matching lines @@
         detectedAspectRatioString += " cropped";
       } else
         detectedAspectRatioString += " letterbox";
 
       console.log("Original image is: " + detectedAspectRatioString);
       callback(detectedAspectRatioString);
     }
   },
                               50);
 }