Remove DOMImplementation.createCSSStyleSheet()

LayoutTests/fast/dom/StyleSheet/gc-parent-rule.html

Index: LayoutTests/fast/dom/StyleSheet/gc-parent-rule.html
diff --git a/LayoutTests/fast/dom/StyleSheet/gc-parent-rule.html b/LayoutTests/fast/dom/StyleSheet/gc-parent-rule.html
index 20337410897123a29a8f4ebb47882f1a72daf4b1..3a8d5b629679f22d7a66beb0f4e35d934ad27c01 100644
--- a/LayoutTests/fast/dom/StyleSheet/gc-parent-rule.html
+++ b/LayoutTests/fast/dom/StyleSheet/gc-parent-rule.html
@@ -7,9 +7,20 @@
 window.jsTestIsAsync = true;
 description("Test that CSS rules don't lose custom properties on GC when only reachable through child rules.");
 
+function createCSSStyleSheet()
+{
+    style = document.createElement("style");
+    document.head.appendChild(style);
+    shouldBeType("style.sheet", "CSSStyleSheet");
+    var sheet = style.sheet;
+    document.head.removeChild(style);
+    shouldBeNull("style.sheet");
+    return sheet;
+}
+
 function test()
 {
-    var sheet = document.implementation.createCSSStyleSheet("title", "screen");
+    var sheet = createCSSStyleSheet();
     sheet.insertRule("@media all { div { color:black } }", 0);
     rule = sheet.rules[0].cssRules[0];
     rule.parentRule.foo = "bar";