fix(Observable): rethrow errors when syncErrorThrowable and inherit it from destination. Fixes #2813

Author: jayphelps

src/Observable.ts

@@ -199,7 +199,7 @@ export class Observable<T> implements Subscribable<T> {
     if (operator) {
       operator.call(sink, this.source);
     } else {
-      sink.add(this.source ? this._subscribe(sink) : this._trySubscribe(sink));
+      sink.add(this.source || !sink.syncErrorThrowable ? this._subscribe(sink) : this._trySubscribe(sink));
     }
 
     if (sink.syncErrorThrowable) {

src/Subscriber.ts

@@ -68,6 +68,7 @@ export class Subscriber<T> extends Subscription implements Observer<T> {
         }
         if (typeof destinationOrNext === 'object') {
           if (destinationOrNext instanceof Subscriber) {
+            this.syncErrorThrowable = destinationOrNext.syncErrorThrowable;
             this.destination = (<Subscriber<any>> destinationOrNext);
             (<any> this.destination).add(this);
           } else {