Re-enable local video test with better logging and higher tolerance.

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;
@@ skipping 48 matching lines @@
               },
               callback);
 }
 
 function detectVideo(videoElementName, predicate, callback) {
   console.log('Looking at video in element ' + videoElementName);
 
   var width = VIDEO_TAG_WIDTH;
   var height = VIDEO_TAG_HEIGHT;
   var videoElement = $(videoElementName);
-  var canvas = $(videoElementName + '-canvas');
   var oldPixels = [];
+  var startTimeMs = new Date().getTime();
   var waitVideo = setInterval(function() {
+    var canvas = $(videoElementName + '-canvas');
+    if (canvas == null) {
+      console.log('Waiting for ' + videoElementName + '-canvas' + ' to appear');
+      return;
+    }
     var context = canvas.getContext('2d');
     context.drawImage(videoElement, 0, 0, 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 (oldPixels.length == pixels.length &&
         predicate(pixels, oldPixels)) {
       console.log('Done looking at video in element ' + videoElementName);
       clearInterval(waitVideo);
       callback(videoElement.videoWidth, videoElement.videoHeight);
     }
     oldPixels = pixels;
+
+    var elapsedTime = new Date().getTime() - startTimeMs;
+    if (elapsedTime > 3000) {
+      startTimeMs = new Date().getTime();
+      console.log('Still waiting for video to satisfy ' + predicate.toString());
+    }
   }, 200);
 }
 
 function waitForVideoWithResolution(element, expected_width, expected_height) {
   addExpectedEvent();
   detectVideoPlaying(element,
       function (width, height) {
         assertEquals(expected_width, width);
         assertEquals(expected_height, height);
         eventOccured();
@@ skipping 84 matching lines @@
 // pixels are changed.
 function isVideoPlaying(pixels, previousPixels) {
   for (var i = 0; i < pixels.length; i++) {
     if (pixels[i] != previousPixels[i]) {
       return true;
     }
   }
   return false;
 }
 
+// Pixels is an array where pixels[0] is the R value for the first pixel,
+// pixels[1] is the G value, and so on.
 function isVideoBlack(pixels) {
   for (var i = 0; i < pixels.length; i++) {
-    // |pixels| is in RGBA. Ignore the alpha channel.
-    // We allow it to be off by 1, to account for rounding errors in YUV
-    // conversion.
-    if (pixels[i] != 0 && pixels[i] != 1 && (i + 1) % 4 != 0) {
+    if ((i + 1) % 4 == 0) {
+      // Ignore the alpha channel.
+      continue;
+    }
+
+    // Should be == 0, but account for rounding errors in YUV conversion.

[kjellander_chromium, 2015/05/12 13:35:46]

Clarify in the comment that a black pixel is == 0. Now it sounds like that is
referring to the condition, which obviously should be > 0 if there were no
rounding errors.

[phoglund_chromium, 2015/05/13 08:47:35]

Done.

+    if (pixels[i] > 3) {
+      console.log('Found nonblack pixel at ' + i + ', was ' + pixels[i]);
       return false;
     }
   }
   return true;
 }
 
 // This function matches |left| and |right| and fails the test if the
 // values don't match using normal javascript equality (i.e. the hard
 // types of the operands aren't checked).
 function assertEquals(expected, actual) {
@@ skipping 17 matching lines @@
       if (device.kind == 'video')
         hasVideoInputDevice = true;
     });
 
     if (hasVideoInputDevice)
       sendValueToTest('has-video-input-device');
     else
       sendValueToTest('no-video-input-devices');
   });
 }