Image Capture: Reject applyConstraints() if passed an unsupported constraint

third_party/WebKit/LayoutTests/imagecapture/MediaStreamTrack-applyConstraints.html

Index: third_party/WebKit/LayoutTests/imagecapture/MediaStreamTrack-applyConstraints.html
diff --git a/third_party/WebKit/LayoutTests/imagecapture/MediaStreamTrack-applyConstraints.html b/third_party/WebKit/LayoutTests/imagecapture/MediaStreamTrack-applyConstraints.html
index 9db07b1b5ca7091d8eaa61a82a97957a5a031dd9..dc9da9b172cff3bd460374b11f49e9d4a3b4ea5d 100644
--- a/third_party/WebKit/LayoutTests/imagecapture/MediaStreamTrack-applyConstraints.html
+++ b/third_party/WebKit/LayoutTests/imagecapture/MediaStreamTrack-applyConstraints.html
@@ -41,18 +41,27 @@ async_test(function(t) {
                                     }]};
 
   var theMock = null;
+  var videoTrack = null;
   mockImageCaptureReady
     .then(mock => {
       theMock = mock;
       var stream = canvas.captureStream();
-      var videoTrack = stream.getVideoTracks()[0];
-
-      return videoTrack.applyConstraints(constraints);
+      videoTrack = stream.getVideoTracks()[0];
+
+      // |videoTrack|'s capabilities gathering, just like the actual capture, is
+      // a process kicked off right after creation, we introduce a small delay
+      // to allow for those to be collected, since they are needed to understand
+      // which constraints are supported in applyConstraints().
+      // TODO(mcasas): this shouldn't be needed, https://crbug.com/711524.
+      return new Promise(resolve => setTimeout(resolve, 100));
     },
     error => {
       assert_unreached("Error creating MockImageCapture: " + error);
     })
     .then(function() {
+      return videoTrack.applyConstraints(constraints);
+    })
+    .then(function() {
       assert_equals(constraints.advanced[0].whiteBalanceMode,
                     meteringModeNames[theMock.options().white_balance_mode],
                     'whiteBalanceMode');