Make Document::styleForElementIgnoringPendingStyleSheets() be aware of a flat tree structure

third_party/WebKit/LayoutTests/fast/css/getComputedStyle/computed-style-redistribution.html

Index: third_party/WebKit/LayoutTests/fast/css/getComputedStyle/computed-style-redistribution.html
diff --git a/third_party/WebKit/LayoutTests/fast/css/getComputedStyle/computed-style-redistribution.html b/third_party/WebKit/LayoutTests/fast/css/getComputedStyle/computed-style-redistribution.html
index ce3e73de39624eae173c943b58d0c73f3076e690..387bcb4b70ab6149d57ab3d185b73f8782361430 100644
--- a/third_party/WebKit/LayoutTests/fast/css/getComputedStyle/computed-style-redistribution.html
+++ b/third_party/WebKit/LayoutTests/fast/css/getComputedStyle/computed-style-redistribution.html
@@ -10,8 +10,8 @@ custom-element { color: red }
 <script>
 description("Check that getComputedStyle causes a shadow re-distribution when necessary.");
 
-var red = "rgb(255, 0, 0)";
 var green = "rgb(0, 128, 0)";
+var white = "rgb(0, 0, 0)";
 
 var custom = document.querySelector("custom-element");
 var shadowRoot = custom.createShadowRoot();
@@ -20,14 +20,12 @@ shadowRoot.innerHTML = '<style>::content div { color: green; }</style><content s
 var d1 = document.querySelector(".d1");
 var d2 = document.querySelector(".d2");
 
-shouldBe("getComputedStyle(d1).color", "red");
+shouldBe("getComputedStyle(d1).color", "white");
 shouldBe("getComputedStyle(d2).color", "green");
 
-document.body.offsetTop;
-
 shadowRoot.querySelector("content").setAttribute("select", ".d1");
 
 shouldBe("getComputedStyle(d1).color", "green");
-shouldBe("getComputedStyle(d2).color", "red");
+shouldBe("getComputedStyle(d2).color", "white");
 
 </script>