CSSStyleDeclaraction returns empty string

LayoutTests/fast/css/resources/parsing-webkit-font-smoothing.js

Index: LayoutTests/fast/css/resources/parsing-webkit-font-smoothing.js
diff --git a/LayoutTests/fast/css/resources/parsing-webkit-font-smoothing.js b/LayoutTests/fast/css/resources/parsing-webkit-font-smoothing.js
index 6ab673453f80c81f3d8e3fb37bd19c02b39e89d9..3f68e0787c2630148e77ce641e86140bd455e9e3 100644
--- a/LayoutTests/fast/css/resources/parsing-webkit-font-smoothing.js
+++ b/LayoutTests/fast/css/resources/parsing-webkit-font-smoothing.js
@@ -5,7 +5,7 @@ function test(value)
     var span = document.createElement("span");
     span.setAttribute("style", value);
     document.body.appendChild(span);
-    
+
     var result = span.style.getPropertyValue("-webkit-font-smoothing");
     document.body.removeChild(span);
     return result;
@@ -16,6 +16,6 @@ shouldBe('test("-webkit-font-smoothing: none;")', '"none"');
 shouldBe('test("-webkit-font-smoothing: antialiased;")', '"antialiased"');
 shouldBe('test("-webkit-font-smoothing: subpixel-antialiased;")', '"subpixel-antialiased"');
 
-shouldBe('test("-webkit-font-smoothing: apple;")', 'null');
-shouldBe('test("-webkit-font-smoothing: 15;")', 'null');
-shouldBe('test("-webkit-font-smoothing: auto auto;")', 'null');
+shouldBeEqualToString('test("-webkit-font-smoothing: apple;")', '');
+shouldBeEqualToString('test("-webkit-font-smoothing: 15;")', '');
+shouldBeEqualToString('test("-webkit-font-smoothing: auto auto;")', '');