Tests that splitting properties when pasting works.

Before pasting:
[expanded] 
element.style { ()
    font-size: 12px;

[expanded] 
div { (user agent stylesheet)
    display: block;

After pasting 'margin-left: 1px':
[expanded] 
element.style { ()
    margin-left: 1px;
    font-size: 12px;

[expanded] 
div { (user agent stylesheet)
    display: block;

After pasting 'margin-top: 1px; color: red;':
[expanded] 
element.style { ()
    margin-left: 1px;
    font-size: 12px;
    margin-top: 1px;
    color: red;

[expanded] 
div { (user agent stylesheet)
    display: block;

After pasting 'foo: bar; moo: zoo' over 'margin-top':
[expanded] 
element.style { ()
    margin-left: 1px;
    font-size: 12px;
/-- overloaded --/     foo: bar;
/-- overloaded --/     moo: zoo;
    color: red;

[expanded] 
div { (user agent stylesheet)
    display: block;