Tests that the "style" attribute removal results in the Styles sidebar pane update (not a crash). Bug 51478

Before style property removal:
[expanded] 
element.style { ()
    color: red;

[expanded] 
div { (user agent stylesheet)
    display: block;
    unicode-bidi: isolate;

After style property removal:
[expanded] 
element.style { ()

[expanded] 
div { (user agent stylesheet)
    display: block;
    unicode-bidi: isolate;