Implement proposed shadow tree cascade order.

LayoutTests/fast/dom/shadow/cascade-of-treeboundary-crossing-rules.html

Index: LayoutTests/fast/dom/shadow/cascade-of-treeboundary-crossing-rules.html
diff --git a/LayoutTests/fast/dom/shadow/cascade-of-treeboundary-crossing-rules.html b/LayoutTests/fast/dom/shadow/cascade-of-treeboundary-crossing-rules.html
index 5d7fadd610e18e40294cc022920ae29917b41cac..8cbd70c837d89e64309d24679b410876396d5539 100644
--- a/LayoutTests/fast/dom/shadow/cascade-of-treeboundary-crossing-rules.html
+++ b/LayoutTests/fast/dom/shadow/cascade-of-treeboundary-crossing-rules.html
@@ -36,18 +36,18 @@ function cleanUp()
 
 description('Test for casacde of treeboundary crossing rules.');
 
-// Rules declared in inner treescope should win.
+// Rules declared in outer treescope should win.
 sandbox.appendChild(
     createDOM('div', {'id': 'host'},
         createDOM('style', {},
-            document.createTextNode('p:empty { border: 1px solid blue; }')),
+            document.createTextNode('p:empty { border: 1px solid green; }')),
         createShadowRoot(
             createDOM('style', {},
                 document.createTextNode('::content > p { border: 1px solid red; }')),
             createDOM('div', {},
                 createShadowRoot(
                     createDOM('style', {},
-                        document.createTextNode('::content > p { border: 1px solid green; }')),
+                        document.createTextNode('::content > p { border: 1px solid blue; }')),
                     createDOM('content', {})),
                 createDOM('content', {}))),
         createDOM('p', {'id': 'target'})));
@@ -103,6 +103,22 @@ borderColorShouldBe('host/target', 'rgb(0, 128, 0)');
 
 cleanUp();
 
+// Comparing important rules declared in outer treescope with important rules declared in inner treescope.
+// Inner's should win.
+sandbox.appendChild(
+    createDOM('div', {},
+        createDOM('style', {},
+            document.createTextNode('div { border: 1px solid red !important; }')),
+        createDOM('div', {'id': 'host'},
+            createShadowRoot(
+                createDOM('style', {},
+                    document.createTextNode('#target { border: 1px solid green !important; }')),
+                createDOM('p', {'id': 'target'})))));
+
+borderColorShouldBe('host/target', 'rgb(0, 128, 0)');
+
+cleanUp();
+
 </script>
 </html>