[css3-text] Implement text-decoration property shorthand

LayoutTests/fast/css/getComputedStyle/computed-style-expected.txt

 Attributes that are exposed in the CSS computed style object:
 
 background-attachment: scroll;
 background-clip: border-box;
 background-color: rgba(0, 0, 0, 0);
 background-image: none;
 background-origin: padding-box;
 background-position: 0% 0%;
 background-repeat: repeat;
 background-size: auto;
@@ skipping 66 matching lines @@
 page-break-before: auto;
 page-break-inside: auto;
 pointer-events: auto;
 position: static;
 resize: none;
 right: auto;
 speak: normal;
 table-layout: auto;
 tab-size: 8;
 text-align: start;
-text-decoration: none;
+text-decoration: none solid rgb(0, 0, 0);
 text-indent: 0px;
 text-rendering: auto;
 text-shadow: none;
 text-overflow: clip;
 text-transform: none;
 top: auto;
 unicode-bidi: normal;
 vertical-align: baseline;
 visibility: visible;
 white-space: normal;
@@ skipping 150 matching lines @@
 
 Other attributes that the computed style class supports:
 
 background-position-x: 0%;
 background-position-y: 0%;
 border-spacing: 0px 0px;
 overflow: visible;
 -webkit-mask-position-x: 0%;
 -webkit-mask-position-y: 0%;