Reland WebRtcBrowserTest.CanSetupVideoCallAndDisableLocalVideo

content/test/data/media/webrtc_test_utilities.js

Index: content/test/data/media/webrtc_test_utilities.js
diff --git a/content/test/data/media/webrtc_test_utilities.js b/content/test/data/media/webrtc_test_utilities.js
index 3d5435938d03ee8cd5d69cc55973b2fdb87b8e46..6e9cde639dcdf5299182c84cb4a785eca4391d13 100644
--- a/content/test/data/media/webrtc_test_utilities.js
+++ b/content/test/data/media/webrtc_test_utilities.js
@@ -52,6 +52,14 @@ function detectVideoStopped(videoElementName, callback) {
               callback);
 }
 
+function detectBlackVideo(videoElementName, callback) {
+  detectVideo(videoElementName,
+              function (pixels, previous_pixels) {
+                return isVideoBlack(pixels);
+              },
+              callback);
+}
+
 function detectVideo(videoElementName, predicate, callback) {
   console.log('Looking at video in element ' + videoElementName);
 
@@ -97,6 +105,11 @@ function waitForVideoToStop(videoElement) {
   detectVideoStopped(videoElement, function () { eventOccured(); });
 }
 
+function waitForBlackVideo(videoElement) {
+  addExpectedEvent();
+  detectBlackVideo(videoElement, function () { eventOccured(); });
+}
+
 // Calculates the current frame rate and compares to |expected_frame_rate|
 // |callback| is triggered with value |true| if the calculated frame rate
 // is +-1 the expected or |false| if five calculations fail to match
@@ -171,6 +184,16 @@ function isVideoPlaying(pixels, previousPixels) {
   return false;
 }
 
+function isVideoBlack(pixels) {
+  for (var i = 0; i < pixels.length; i++) {
+    // |pixels| is in RGBA. Ignore the alpha channel.
+    if (pixels[i] != 0 && (i + 1) % 4 != 0) {
+      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).