fix(element binder): fix memory leak with expando value holding onto …

…node

Expando keys are weak references but the values are not.  The
ElementProbe value holds strong references to the node and the injector
keep it from being garbage collected.

lib/core_dom/element_binder.dart

@@ -319,6 +319,7 @@ class ElementBinder {
     nodeInjector = parentInjector.createChild([nodeModule]);
     probe = _expando[node] = new ElementProbe(
         parentInjector.getByKey(_ELEMENT_PROBE_KEY), node, nodeInjector, scope);
+    scope.on(ScopeEvent.DESTROY).listen((_) {_expando[node] = null;});
 
     _link(nodeInjector, probe, scope, nodeAttrs, formatters);
 

lib/core_dom/shadow_dom_component_factory.dart

@@ -179,17 +179,18 @@ class _ComponentFactory implements Function {
 
   Injector createShadowInjector(injector, TemplateLoader templateLoader) {
     var probe;
-   var shadowModule = new Module()
+    var shadowModule = new Module()
       ..bindByKey(typeKey)
       ..bindByKey(_NG_ELEMENT_KEY)
       ..bindByKey(_EVENT_HANDLER_KEY, toImplementation: ShadowRootEventHandler)
       ..bindByKey(_SCOPE_KEY, toValue: shadowScope)
       ..bindByKey(_TEMPLATE_LOADER_KEY, toValue: templateLoader)
       ..bindByKey(_SHADOW_ROOT_KEY, toValue: shadowDom)
       ..bindByKey(_ELEMENT_PROBE, toFactory: (_) => probe);
-      shadowInjector = injector.createChild([shadowModule], name: SHADOW_DOM_INJECTOR_NAME);
+    shadowInjector = injector.createChild([shadowModule], name: SHADOW_DOM_INJECTOR_NAME);
     probe = _expando[shadowDom] = new ElementProbe(
         injector.getByKey(_ELEMENT_PROBE), shadowDom, shadowInjector, shadowScope);
+    shadowScope.on(ScopeEvent.DESTROY).listen((ScopeEvent) {_expando[shadowDom] = null;});
     return shadowInjector;
   }
 }

test/core_dom/compiler_spec.dart

@@ -727,6 +727,28 @@ void main() {
             expect(_.rootElement.shadowRoot).toBeNotNull();
           }
         }));
+
+        describe('expando memory', () {
+          Expando expando;
+
+          beforeEach(inject((Expando _expando) => expando = _expando));
+
+          ['shadowy', 'shadowless'].forEach((selector) {
+            it('should release expando when a node is freed ($selector)', async(() {
+              _.rootScope.context['flag'] = true;
+              _.compile('<div><div ng-if=flag><$selector>x</$selector></div></div>');
+              microLeap(); _.rootScope.apply();
+              var element = _.rootElement.querySelector('$selector');
+              if (element.shadowRoot != null) {
+                element = element.shadowRoot;
+              }
+              expect(expando[element]).not.toEqual(null);
+              _.rootScope.context['flag'] = false;
+              microLeap(); _.rootScope.apply();
+              expect(expando[element]).toEqual(null);
+            }));
+          });
+        });
       });
 
       describe('bindings', () {
@@ -849,7 +871,6 @@ void main() {
         expect(_.rootElement.text).toEqual('MyController');
       });
     });
-
   }));
 }
 
@@ -975,6 +996,16 @@ class SimpleComponent {
   }
 }
 
+@Component(
+    selector: 'simple2',
+    template: r'{{name}}(<content>SHADOW-CONTENT</content>)')
+class Simple2Component {
+  Scope scope;
+  Simple2Component(Scope this.scope) {
+    scope.context['name'] = 'INNER';
+  }
+}
+
 @Component(
   selector: 'shadowy',
   template: r'With shadow DOM',