Move backgroundColorOf/backgroundColorShouldBe to shadow-dom.js

LayoutTests/fast/dom/shadow/delegatesFocus-highlight-sibling.html

Index: LayoutTests/fast/dom/shadow/delegatesFocus-highlight-sibling.html
diff --git a/LayoutTests/fast/dom/shadow/delegatesFocus-highlight-sibling.html b/LayoutTests/fast/dom/shadow/delegatesFocus-highlight-sibling.html
index 21cfd8ef7dada61c9817e1e17760c8aed86bd374..e3132637c81ecd8344303c44babefd91a79e5e0d 100644
--- a/LayoutTests/fast/dom/shadow/delegatesFocus-highlight-sibling.html
+++ b/LayoutTests/fast/dom/shadow/delegatesFocus-highlight-sibling.html
@@ -55,14 +55,6 @@ function RegisterXMenu() {
   });
 }
 
-function backgroundColorOf(selector) {
-    return window.getComputedStyle(getNodeInTreeOfTrees(selector)).backgroundColor;
-}
-
-function backgroundColorShouldBe(selector, expected) {
-    shouldBeEqualToString('backgroundColorOf(\'' + selector + '\')', expected);
-}
-
 function test() {
     debug("crbug/474687 :focus style should properly be applied to shadow hosts.");