refactor(async): refactor EventEmitter

Refactor EventEmitter and Async Facade to match ES7 Observable semantics, properly use RxJS typedefs, make EventEmitter inherit from RxJS Subject. Closes #4149.

BREAKING CHANGE:
- consumers of EventEmitter no longer need to call .toRx()
- EventEmitter is now generic and requires a type - e.g. `EventEmitter<string>`
- EventEmitter and Observable now use the `.subscribe(generatorOrNext, error, complete)` method instead of `.observer(generator)`
- ObservableWrapper uses `callNext/callError/callComplete` instead of `callNext/callThrow/callReturn`

modules/angular2/test/web_workers/shared/mock_event_emitter.dart

@@ -4,7 +4,7 @@ import 'dart:core';
 import 'dart:async';
 import "package:angular2/src/core/facade/async.dart";
 
-class MockEventEmitter extends EventEmitter {
+class MockEventEmitter<T> extends EventEmitter<T> {
   final controller = new StreamController.broadcast(sync: true);
 
   @override

modules/angular2/test/web_workers/shared/mock_event_emitter.ts

@@ -1,11 +1,11 @@
 import {EventEmitter} from 'angular2/src/core/facade/async';
 
-export class MockEventEmitter extends EventEmitter {
+export class MockEventEmitter<T> extends EventEmitter<T> {
   private _nextFns: Function[] = [];
 
   constructor() { super(); }
 
-  observer(generator: any): any {
+  subscribe(generator: any): any {
     this._nextFns.push(generator.next);
     return new MockDisposable();
   }

modules/angular2/test/web_workers/shared/web_worker_test_util.ts

@@ -13,11 +13,11 @@ import {NgZone} from 'angular2/src/core/zone/ng_zone';
  * Such that whatever goes into one's sink comes out the others source.
  */
 export function createPairedMessageBuses(): PairedMessageBuses {
-  var firstChannels: {[key: string]: MockEventEmitter} = {};
+  var firstChannels: {[key: string]: MockEventEmitter<any>} = {};
   var workerMessageBusSink = new MockMessageBusSink(firstChannels);
   var uiMessageBusSource = new MockMessageBusSource(firstChannels);
 
-  var secondChannels: {[key: string]: MockEventEmitter} = {};
+  var secondChannels: {[key: string]: MockEventEmitter<any>} = {};
   var uiMessageBusSink = new MockMessageBusSink(secondChannels);
   var workerMessageBusSource = new MockMessageBusSource(secondChannels);
 
@@ -30,7 +30,7 @@ export class PairedMessageBuses {
 }
 
 export class MockMessageBusSource implements MessageBusSource {
-  constructor(private _channels: {[key: string]: MockEventEmitter}) {}
+  constructor(private _channels: {[key: string]: MockEventEmitter<any>}) {}
 
   initChannel(channel: string, runInZone = true) {
     if (!StringMapWrapper.contains(this._channels, channel)) {
@@ -38,7 +38,7 @@ export class MockMessageBusSource implements MessageBusSource {
     }
   }
 
-  from(channel: string): MockEventEmitter {
+  from(channel: string): MockEventEmitter<any> {
     if (!StringMapWrapper.contains(this._channels, channel)) {
       throw new BaseException(`${channel} is not set up. Did you forget to call initChannel?`);
     }
@@ -49,7 +49,7 @@ export class MockMessageBusSource implements MessageBusSource {
 }
 
 export class MockMessageBusSink implements MessageBusSink {
-  constructor(private _channels: {[key: string]: MockEventEmitter}) {}
+  constructor(private _channels: {[key: string]: MockEventEmitter<any>}) {}
 
   initChannel(channel: string, runInZone = true) {
     if (!StringMapWrapper.contains(this._channels, channel)) {
@@ -57,7 +57,7 @@ export class MockMessageBusSink implements MessageBusSink {
     }
   }
 
-  to(channel: string): MockEventEmitter {
+  to(channel: string): MockEventEmitter<any> {
     if (!StringMapWrapper.contains(this._channels, channel)) {
       this._channels[channel] = new MockEventEmitter();
     }
@@ -79,9 +79,9 @@ export class MockMessageBus extends MessageBus {
     this.source.initChannel(channel, runInZone);
   }
 
-  to(channel: string): MockEventEmitter { return this.sink.to(channel); }
+  to(channel: string): MockEventEmitter<any> { return this.sink.to(channel); }
 
-  from(channel: string): MockEventEmitter { return this.source.from(channel); }
+  from(channel: string): MockEventEmitter<any> { return this.source.from(channel); }
 
   attachToZone(zone: NgZone) {}
 }