Setting HTMLMediaElement.controller does not properly remove the 'mediagroup' content attribute

LayoutTests/media/media-controller-expected.txt

  
 Test presence of MediaController constructor, controller, and mediaGroup attributes:
 EXPECTED (typeof(MediaController) != 'undefined') OK
 EXPECTED (video.controller == 'null') OK
 EXPECTED (video.mediaGroup == '') OK
 
 Test that the presence of a mediaGroup attribute creates a controller:
 EXPECTED (video2.mediaGroup == 'group') OK
 EXPECTED (video2.controller != 'null') OK
 
 Test that setting mediaGroup to an empty string removes the controller:
 RUN(video.mediaGroup = '')
 EXPECTED (video.controller == 'null') OK
 
 Test manually creating and assigning a controller to a media element:
 RUN(controller = new MediaController())
 RUN(video.controller = controller)
 EXPECTED (video.controller == '[object MediaController]') OK
 
 Test assigning the wrong type to the controller attribute of a media element:
-TEST(video.controller = 42) THROWS("TypeError: Value is not of type MediaController") OK
+TEST(video.controller = 42) THROWS("TypeError: Failed to set the 'controller' property on 'HTMLMediaElement': The provided value is not of type 'MediaController'.") OK
 EXPECTED (video.controller == '[object MediaController]') OK
 
 Test assigning a null controller to a media element:
 RUN(video.controller = null)
 EXPECTED (video.controller == 'null') OK
 
 Test that two media elements with the same mediaGroup have the same controller:
 RUN(video.mediaGroup = 'group')
 RUN(video2.mediaGroup = 'group')
 EXPECTED (video.controller === video2.controller == 'true') OK
+
+Test that setting the controller clears the mediaGroup:
+EXPECTED (video.mediaGroup == 'group') OK
+RUN(video.controller = null)
+EXPECTED (video.controller == 'null') OK
+EXPECTED (video.hasAttribute('mediaGroup') == 'false') OK
+EXPECTED (video.mediaGroup == '') OK
+RUN(video.mediaGroup = 'group')
+EXPECTED (video.mediaGroup == 'group') OK
+RUN(video.controller = controller)
+EXPECTED (video.controller == '[object MediaController]') OK
+EXPECTED (video.hasAttribute('mediaGroup') == 'false') OK
+EXPECTED (video.mediaGroup == '') OK
+
+Test that setting the controller to undefined is treated as null:
+EXPECTED (video.controller != 'null') OK
+RUN(video.controller = undefined)
+EXPECTED (video.controller == 'null') OK
 END OF TEST