[CSS Shapes] shape-margin in percentage units always computes to 0px

LayoutTests/fast/shapes/parsing/parsing-test-utils.js

 // Valid values for both shape-inside and shape-outside. Two values are specified when the shape property value
 // differs from the specified value. Three values are specified when the computed shape property value differs
 // from the specified value.
 // eg: "specified value/CSS Text value/computed style value"
 // or: ["specified value", "CSS Text value/computed style value"]
 // or: ["specified value", "CSS Text value", "Computed style value"]
 var validShapeValues = [
     "none",
 
     "inset(10px)",
@@ skipping 152 matching lines @@
 
 // Valid length values for shape-margin and shape-padding.
 var validShapeLengths = [
     "1.5ex",
     "2em",
     "2.5in",
     "3cm",
     "3.5mm",
     "4pt",
     "4.5pc",
-    "5px"
+    "5px",
+    "120%"
 ];
 
 // Invalid length values for shape-margin and shape-padding.
 var invalidShapeLengths = [
     "-5px",
     "none",
-    "120%",
     "\'string\'"
 ];
 
 function getCSSText(property, value)
 {
     var element = document.createElement("div");
     element.style.cssText = property + ": " + value;
     return element.style[property];
 }
 
@@ skipping 71 matching lines @@
 
 function testNotInheritedShapeProperty(property, parentValue, childValue, expectedValue)
 {
     shouldBeEqualToString('getParentAndChildComputedStylesString("' + property + '", "' + parentValue + '", "' + childValue + '")', expectedValue);
 }
 
 function applyToEachArglist(testFunction, arglists)
 {
     arglists.forEach(function(arglist, i, a) {testFunction.apply(null, arglist);});
 }