BREAKING CHANGE:
toPromise is no longer an instance method of the `Observable` returned
by Angular, and fromPromise is no longer available as a static method.
The easiest way to account for this change in applications is to import
the auto-patching modules from rxjs, which will automatically add these
operators back to the Observable prototype.
```
import 'rxjs/add/operator/toPromise';
import 'rxjs/add/observable/fromPromise';
```
Closes#5542Closes#5626
c39f4c3b38