DevTools: make ElementsTreeOutline shadow dom-based.

LayoutTests/inspector/elements/edit-dom-test.js

 function initialize_EditDOMTests()
 {
 
 InspectorTest.doAddAttribute = function(testName, dataNodeId, attributeText, next)
 {
     InspectorTest.domActionTestForNodeId(testName, dataNodeId, testBody, next);
 
     function testBody(node, done)
     {
         var editorElement = InspectorTest.editNodePart(node, "webkit-html-attribute");
         editorElement.dispatchEvent(InspectorTest.createKeyEvent("U+0009")); // Tab
 
         InspectorTest.runAfterPendingDispatches(testContinuation);
 
         function testContinuation()
         {
-            var editorElement = window.getSelection().anchorNode.parentElement;
+            var editorElement = WebInspector.panels.elements._treeOutlines[0]._shadowRoot.getSelection().anchorNode.parentElement;
             editorElement.textContent = attributeText;
             editorElement.dispatchEvent(InspectorTest.createKeyEvent("Enter"));
             InspectorTest.addSniffer(WebInspector.ElementsTreeUpdater.prototype, "_updateModifiedNodes", done);
         }
     }
 }
 
 InspectorTest.domActionTestForNodeId = function(testName, dataNodeId, testBody, next)
 {
     function callback(testNode, continuation)
@@ skipping 44 matching lines @@
     var editorElement = InspectorTest.editNodePart(node, className);
     editorElement.textContent = newValue;
     editorElement.dispatchEvent(InspectorTest.createKeyEvent("Enter"));
     if (useSniffer)
         InspectorTest.addSniffer(WebInspector.ElementsTreeUpdater.prototype, "_updateModifiedNodes", step2);
     else
         InspectorTest.runAfterPendingDispatches(step2);
 }
 
 }