refactor(ErrorObservable): clarify an error type E for ErrorObserva…

…ble.

BREAKING CHANGE - `ErrorObservable.create()` (`Obserbable.throw()`)
takes a new type parameter `E` that express a error type instead on old
one's `T`. Their functions return `ErrorObservable<E>`.
It is still the drived type of `Observable<any>`, it's not changed from
old one. But it contains the error typed as `E` now.

src/observable/ErrorObservable.ts

@@ -12,7 +12,7 @@ export interface DispatchArg {
  * @extends {Ignored}
  * @hide true
  */
-export class ErrorObservable extends Observable<any> {
+export class ErrorObservable<E> extends Observable<any> {
 
  /**
  * Creates an Observable that emits no items to the Observer and immediately
@@ -54,7 +54,7 @@ export class ErrorObservable extends Observable<any> {
  * @name throw
  * @owner Observable
  */
- static create<T>(error: any, scheduler?: Scheduler) {
+ static create<E>(error: E, scheduler?: Scheduler): ErrorObservable<E> {
  return new ErrorObservable(error, scheduler);
  }
 
@@ -63,7 +63,7 @@ export class ErrorObservable extends Observable<any> {
  subscriber.error(error);
  }
 
- constructor(public error: any, private scheduler?: Scheduler) {
+ constructor(public error: E, private scheduler?: Scheduler) {
  super();
  }