bindings: Adds check for attributes on prototype chains in CSSStyleDeclaration.

LayoutTests/fast/dom/CSSStyleDeclaration/css-style-declaration-named-setter.html

Index: LayoutTests/fast/dom/CSSStyleDeclaration/css-style-declaration-named-setter.html
diff --git a/LayoutTests/fast/dom/CSSStyleDeclaration/css-style-declaration-named-setter.html b/LayoutTests/fast/dom/CSSStyleDeclaration/css-style-declaration-named-setter.html
index a7186cc38b3edd16e1c72b757c9fe5ae3927efda..d8cba2077884edb2d73cfc2cf7877d837b17d675 100644
--- a/LayoutTests/fast/dom/CSSStyleDeclaration/css-style-declaration-named-setter.html
+++ b/LayoutTests/fast/dom/CSSStyleDeclaration/css-style-declaration-named-setter.html
@@ -9,16 +9,17 @@ shouldBeEqualToString("document.body.style.margin", "0px");
 shouldBe("document.body.style.margin = 1", "1");
 shouldBeEqualToString("document.body.style.margin", "1px");
 
-shouldBe("document.body.style.__proto__.margin = 777", "777");
-shouldBe("document.body.style.__proto__.margin", "777");
-
-shouldBeEqualToString("document.body.style.margin", "1px");
-shouldBe("document.body.style.margin = 2", "2");
-shouldBeEqualToString("document.body.style.margin", "2px");
-
 var badString = { toString: function() { throw "Exception in toString()"; } };
 shouldThrow("document.body.style.margin = badString", "'Exception in toString()'");
-shouldBeEqualToString("document.body.style.margin", "2px"); // Should not reset the previous value.
+shouldBeEqualToString("document.body.style.margin", "1px"); // Should not reset the previous value.
+
+// Creating a new property on prototype shadows the named property.
+shouldBe("document.body.style.__proto__.margin = 2", "2");
+shouldBe("document.body.style.__proto__.margin", "2");
+shouldBeEqualToNumber("document.body.style.margin", 2);
+
+shouldBe("document.body.style.margin = 3", "3");
+shouldBeEqualToNumber("document.body.style.margin", 3);
 
 </script>
 </body>