Add the named color `rebeccapurple` (#639)

LayoutTests/fast/css/named-colors.html

Index: LayoutTests/fast/css/named-colors.html
diff --git a/LayoutTests/fast/css/named-colors.html b/LayoutTests/fast/css/named-colors.html
index 55018cf34221fc5490592b7bb39ac550130a461e..2d4de735689292987acb284082c7c8caeb03fa0f 100644
--- a/LayoutTests/fast/css/named-colors.html
+++ b/LayoutTests/fast/css/named-colors.html
@@ -6,9 +6,9 @@
 
     if (window.testRunner)
         testRunner.dumpAsText();
-        
-    // Named colors and their rgb values as per the css3 specification.
-    // http://www.w3.org/TR/css3-color/#svg-color
+
+    // Named colors and their rgb values as per the CSS Color specification.
+    // http://dev.w3.org/csswg/css-color/#named-colors
     var colors = [
         ['aliceblue', '240,248,255'],
         ['antiquewhite', '250,235,215'],
@@ -129,6 +129,7 @@
         ['plum', '221,160,221'],
         ['powderblue', '176,224,230'],
         ['purple', '128,0,128'],
+        ['rebeccapurple', '102,51,153'],
         ['red', '255,0,0'],
         ['rosybrown', '188,143,143'],
         ['royalblue', '65,105,225'],
@@ -169,7 +170,7 @@
         colorSpan.style.backgroundColor = colorName;
         element.appendChild(colorSpan);
         document.body.appendChild(element);
-        
+
         var value = document.defaultView.getComputedStyle(colorSpan, "").getPropertyValue("background-color");
         var actual = value.match(/rgb\((\d+),\s*(\d+),\s*(\d+)\)/).splice(1).join(',');
         if (actual == expected) {