fix(core): always remove DOM listeners and stream subscriptions

This is needed to prevent memory leaks. The DOM
listeners don’t need to be removed for simple examples,
but a big internal app shows memory leaks because of them.

BREAKING CHANGE:
- `Renderer.listen` now has to return a function that
  removes the event listener.

modules/angular2/src/core/change_detection/abstract_change_detector.ts

@@ -17,7 +17,7 @@ import {Locals} from './parser/locals';
 import {ChangeDetectionStrategy, ChangeDetectorState} from './constants';
 import {wtfCreateScope, wtfLeave, WtfScopeFn} from '../profile/profile';
 import {isObservable} from './observable_facade';
-
+import {ObservableWrapper} from 'angular2/src/facade/async';
 
 var _scope_check: WtfScopeFn = wtfCreateScope(`ChangeDetector#check(ascii id, bool throwOnChange)`);
 
@@ -40,6 +40,7 @@ export class AbstractChangeDetector<T> implements ChangeDetector {
   mode: ChangeDetectionStrategy = null;
   pipes: Pipes = null;
   propertyBindingIndex: number;
+  outputSubscriptions: any[];
 
   // This is an experimental feature. Works only in Dart.
   subscriptions: any[];
@@ -72,7 +73,7 @@ export class AbstractChangeDetector<T> implements ChangeDetector {
 
   handleEvent(eventName: string, elIndex: number, event: any): boolean {
     if (!this.hydrated()) {
-      return true;
+      this.throwDehydratedError();
     }
     try {
       var locals = new Map<string, any>();
@@ -180,6 +181,8 @@ export class AbstractChangeDetector<T> implements ChangeDetector {
       this._unsubsribeFromObservables();
     }
 
+    this._unsubscribeFromOutputs();
+
     this.dispatcher = null;
     this.context = null;
     this.locals = null;
@@ -258,6 +261,15 @@ export class AbstractChangeDetector<T> implements ChangeDetector {
     }
   }
 
+  private _unsubscribeFromOutputs(): void {
+    if (isPresent(this.outputSubscriptions)) {
+      for (var i = 0; i < this.outputSubscriptions.length; ++i) {
+        ObservableWrapper.dispose(this.outputSubscriptions[i]);
+        this.outputSubscriptions[i] = null;
+      }
+    }
+  }
+
   // This is an experimental feature. Works only in Dart.
   observeValue(value: any, index: number): any {
     if (isObservable(value)) {

modules/angular2/src/core/change_detection/codegen_logic_util.ts

@@ -153,6 +153,7 @@ export class CodegenLogicUtil {
 
   genHydrateDirectives(directiveRecords: DirectiveRecord[]): string {
     var res = [];
+    var outputCount = 0;
     for (var i = 0; i < directiveRecords.length; ++i) {
       var r = directiveRecords[i];
       var dirVarName = this._names.getDirectiveName(r.directiveIndex);
@@ -160,14 +161,24 @@ export class CodegenLogicUtil {
       if (isPresent(r.outputs)) {
         r.outputs.forEach(output => {
           var eventHandlerExpr = this._genEventHandler(r.directiveIndex.elementIndex, output[1]);
+          var statementStart =
+              `this.outputSubscriptions[${outputCount++}] = ${dirVarName}.${output[0]}`;
           if (IS_DART) {
-            res.push(`${dirVarName}.${output[0]}.listen(${eventHandlerExpr});`);
+            res.push(`${statementStart}.listen(${eventHandlerExpr});`);
           } else {
-            res.push(`${dirVarName}.${output[0]}.subscribe({next: ${eventHandlerExpr}});`);
+            res.push(`${statementStart}.subscribe({next: ${eventHandlerExpr}});`);
           }
         });
       }
     }
+    if (outputCount > 0) {
+      var statementStart = 'this.outputSubscriptions';
+      if (IS_DART) {
+        res.unshift(`${statementStart} = new List(${outputCount});`);
+      } else {
+        res.unshift(`${statementStart} = new Array(${outputCount});`);
+      }
+    }
     return res.join("\n");
   }
 

modules/angular2/src/core/change_detection/dynamic_change_detector.ts

@@ -114,6 +114,7 @@ export class DynamicChangeDetector extends AbstractChangeDetector<any> {
         super.observeDirective(this._getDirectiveFor(index), i);
       }
     }
+    this.outputSubscriptions = [];
     for (var i = 0; i < this._directiveRecords.length; ++i) {
       var r = this._directiveRecords[i];
       if (isPresent(r.outputs)) {
@@ -122,7 +123,8 @@ export class DynamicChangeDetector extends AbstractChangeDetector<any> {
               <any>this._createEventHandler(r.directiveIndex.elementIndex, output[1]);
           var directive = this._getDirectiveFor(r.directiveIndex);
           var getter = reflector.getter(output[0]);
-          ObservableWrapper.subscribe(getter(directive), eventHandler);
+          this.outputSubscriptions.push(
+              ObservableWrapper.subscribe(getter(directive), eventHandler));
         });
       }
     }

modules/angular2/src/core/change_detection/exceptions.ts

@@ -91,7 +91,7 @@ export class ChangeDetectionError extends WrappedException {
  * This is an internal Angular error.
  */
 export class DehydratedException extends BaseException {
-  constructor() { super('Attempt to detect changes on a dehydrated detector.'); }
+  constructor() { super('Attempt to use a dehydrated detector.'); }
 }
 
 /**