FaceDetection: add support for <video> input

third_party/WebKit/LayoutTests/shapedetection/detectface-HTMLImageElement.html

Index: third_party/WebKit/LayoutTests/shapedetection/detectface-HTMLImageElement.html
diff --git a/third_party/WebKit/LayoutTests/shapedetection/detectface-HTMLImageElement.html b/third_party/WebKit/LayoutTests/shapedetection/detectface-HTMLImageElement.html
index a7723a6908a3732aa346a43b5bfc63456ca43f4e..e94e1eb83ca004b32384618d156fc04d6f827682 100644
--- a/third_party/WebKit/LayoutTests/shapedetection/detectface-HTMLImageElement.html
+++ b/third_party/WebKit/LayoutTests/shapedetection/detectface-HTMLImageElement.html
@@ -8,8 +8,8 @@
 </body>
 <script>
 
-// This test verifies that FaceDetector can detect(HTMLImageElement). Uses the
-// mock mojo server implemented in mock-shapedetection.js.
+// This test verifies that FaceDetector.detect works on an HTMLImageElement.
+// Uses the mock mojo server implemented in mock-shapedetection.js.
 async_test(function(t) {
   var img = document.getElementById("img");
 
@@ -27,11 +27,10 @@ async_test(function(t) {
     })
     .then(faceDetectionResult => {
       const imageReceivedByMock = theMock.getFrameData();
-      assert_equals(imageReceivedByMock.byteLength, 2500,
-                    "imageReceivedByMock.byteLength");
+      assert_equals(imageReceivedByMock.byteLength, 2500, "Image length");
       const GREEN_PIXEL = 0xFF00FF00;
-      assert_equals(imageReceivedByMock[0], GREEN_PIXEL, "pixel must be green");
-      assert_equals(faceDetectionResult.length, 3, "faceDetectionResult.length");
+      assert_equals(imageReceivedByMock[0], GREEN_PIXEL, "Pixel color");
+      assert_equals(faceDetectionResult.length, 3, "Number of faces");
       t.done();
     })
     .catch(error => {