feat(testability): findBindings and findModels should descend into the ShadowDOM

Note that this won't work for you unless you have a chromedriver build
that works with the shadow DOM.

Author: chirayuk

example/web/animation/repeat_demo.dart

@@ -2,7 +2,7 @@ part of animation;
 
 @Component(
     selector: 'repeat-demo',
-    useShadowDom: false,
+    useShadowDom: true,
     template: '''
       <div class="repeat-demo">
       <button ng-click="ctrl.addItem()">Add Thing</button>

example/web/animation/visibility_demo.dart

@@ -16,8 +16,7 @@ part of animation;
       </div>
       </div>
     ''',
-    publishAs: 'ctrl',
-    useShadowDom: false)
+    publishAs: 'ctrl')
 class VisibilityDemo {
   bool visible = false;
 }

lib/introspection.dart

@@ -28,7 +28,11 @@ ElementProbe _findProbeWalkingUp(dom.Node node, [dom.Node ascendUntil]) {
   while (node != null && node != ascendUntil) {
     var probe = elementExpando[node];
     if (probe != null) return probe;
-    node = node.parent;
+    if (node is dom.ShadowRoot) {
+      node = (node as dom.ShadowRoot).host;
+    } else {
+      node = node.parentNode;
+    }
   }
   return null;
 }
@@ -40,6 +44,14 @@ _walkProbesInTree(dom.Node node, Function walker) {
     for (var child in node.childNodes) {
       _walkProbesInTree(child, walker);
     }
+    if (node is dom.Element) {
+      var shadowRoot = (node as dom.Element).shadowRoot;
+      if (shadowRoot != null) {
+        for (var child in shadowRoot.childNodes) {
+          _walkProbesInTree(child, walker);
+        }
+      }
+    }
   }
 }