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

Author: chirayuk

lib/core_dom/element_binder.dart

@@ -318,6 +318,7 @@ class ElementBinder {
     nodeInjector = parentInjector.createChild([nodeModule]);
     probe = _expando[node] = new ElementProbe(
         parentInjector.get(ElementProbe), 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

@@ -142,6 +142,7 @@ class _ComponentFactory implements Function {
     shadowInjector = injector.createChild([shadowModule], name: SHADOW_DOM_INJECTOR_NAME);
     probe = _expando[shadowDom] = new ElementProbe(
         injector.get(ElementProbe), shadowDom, shadowInjector, shadowScope);
+    shadowScope.on(ScopeEvent.DESTROY).listen((ScopeEvent) {_expando[shadowDom] = null;});
     return shadowInjector;
   }
 }