Tests that adding a property is undone properly.

=== Last property ===
(Initial value)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    font-weight: bold;

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

(After adding property)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    font-weight: bold;
    margin-left: 2px;

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

(After undo)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    font-weight: bold;

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

(After redo)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    font-weight: bold;
    margin-left: 2px;

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

=== First property ===
(Initial value)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    font-weight: bold;
    margin-left: 2px;

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

(After adding property)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    margin-top: 0px;
    font-weight: bold;
    margin-left: 2px;

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

(After undo)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    font-weight: bold;
    margin-left: 2px;

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

(After redo)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    margin-top: 0px;
    font-weight: bold;
    margin-left: 2px;

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

=== Middle property ===
(Initial value)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    margin-top: 0px;
    font-weight: bold;
    margin-left: 2px;

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

(After adding property)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    margin-top: 0px;
    margin-right: 1px;
    font-weight: bold;
    margin-left: 2px;

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

(After undo)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    margin-top: 0px;
    font-weight: bold;
    margin-left: 2px;

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

(After redo)
[expanded] 
element.style { ()

[expanded] 
.container { (<style>)
    margin-top: 0px;
    margin-right: 1px;
    font-weight: bold;
    margin-left: 2px;

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