Version: 51 canary
OS: All

What steps will reproduce the problem?
(1) open http://w3c-test.org/html/semantics/embedded-content/the-img-element/Image-constructor.html

What is the expected output? What do you see instead?
Expected: the second test shows "PASS"
Actual: the second test shows "FAIL"

Please use labels and text to provide additional information.
It's just |assert_true(Image.prototype === HTMLImageElement.prototype);|

Though Firefox and Edge pass the test, real world impact should be low.