perf(render): only create LightDom instances if the element has children

modules/angular2/test/render/dom/dom_renderer_integration_spec.ts

@@ -70,6 +70,25 @@ export function main() {
              });
        }));
 
+    it('should not create LightDom instances if the host element is empty',
+       inject([AsyncTestCompleter, DomTestbed], (async, tb) => {
+         tb.compileAll([
+             someComponent,
+             new ViewDefinition({
+                 componentId: 'someComponent', template: '<some-comp>  <!-- comment -->\n </some-comp>',
+                 directives: [someComponent]
+             })
+           ])
+             .then((protoViewDtos) => {
+               var rootView = tb.createRootView(protoViewDtos[0]);
+               var cmpView = tb.createComponentView(rootView.viewRef, 0, protoViewDtos[1]);
+               expect(cmpView.rawView.proto.elementBinders[0].componentId).toBe('someComponent');
+               expect(cmpView.rawView.boundElements[0].lightDom).toBe(null);
+
+               async.done();
+             });
+       }));
+
     it('should update text nodes', inject([AsyncTestCompleter, DomTestbed], (async, tb) => {
          tb.compileAll([
              someComponent,

modules/angular2/test/render/dom/view/view_spec.ts

@@ -48,20 +48,24 @@ export function main() {
       return new DomView(pv, [DOM.childNodes(root)[0]], [], boundElements);
     }
 
+    function createElementBinder(parentIndex:number = 0, distanceToParent:number = 1) {
+      return new ElementBinder({parentIndex: parentIndex, distanceToParent:distanceToParent, textNodeIndices:[]});
+    }
+
     describe('getDirectParentElement', () => {
 
       it('should return the DomElement of the direct parent', () => {
         var pv = createProtoView(
-            [new ElementBinder(), new ElementBinder({parentIndex: 0, distanceToParent: 1})]);
+            [createElementBinder(), createElementBinder(0, 1)]);
         var view = createView(pv, 2);
         expect(view.getDirectParentElement(1)).toBe(view.boundElements[0]);
       });
 
       it('should return null if the direct parent is not bound', () => {
         var pv = createProtoView([
-          new ElementBinder(),
-          new ElementBinder(),
-          new ElementBinder({parentIndex: 0, distanceToParent: 2})
+          createElementBinder(),
+          createElementBinder(),
+          createElementBinder(0,2)
         ]);
         var view = createView(pv, 3);
         expect(view.getDirectParentElement(2)).toBe(null);