fix(docs-infra): workaround for broken 'import as'

It's unclear why `import as` results in the aliases to be undefined.

Plain tsc seems to do the right thing and emits the correct code, so it
might be some kind of interaction in @angular/cli or webpack that are
causing the failure.

This should be investigated separately from the tsc update in
angular/angular. See angular/angular-cli#13212

Author: IgorMinar

aio/src/app/custom-elements/code/pretty-printer.service.ts

@@ -1,6 +1,6 @@
 import { Injectable } from '@angular/core';
 
-import { from as fromPromise, Observable } from 'rxjs';
+import { from, Observable } from 'rxjs';
 import { first, map, share } from 'rxjs/operators';
 
 import { Logger } from 'app/shared/logger.service';
@@ -20,7 +20,7 @@ export class PrettyPrinter {
   private prettyPrintOne: Observable<PrettyPrintOne>;
 
   constructor(private logger: Logger) {
-    this.prettyPrintOne = fromPromise(this.getPrettyPrintOne()).pipe(share());
+    this.prettyPrintOne = from(this.getPrettyPrintOne()).pipe(share());
   }
 
   private getPrettyPrintOne(): Promise<PrettyPrintOne> {

aio/src/app/custom-elements/elements-loader.ts

@@ -5,9 +5,10 @@ import {
   NgModuleRef,
 } from '@angular/core';
 import { ELEMENT_MODULE_PATHS_TOKEN } from './element-registry';
-import { from as fromPromise, Observable, of } from 'rxjs';
+import { from, Observable, of } from 'rxjs';
 import { createCustomElement } from '@angular/elements';
 
+
 @Injectable()
 export class ElementsLoader {
   /** Map of unregistered custom elements and their respective module paths to load. */
@@ -34,7 +35,7 @@ export class ElementsLoader {
 
     // Returns observable that completes when all discovered elements have been registered.
     const allRegistered = Promise.all(unregisteredSelectors.map(s => this.loadCustomElement(s)));
-    return fromPromise(allRegistered.then(() => undefined));
+    return from(allRegistered.then(() => undefined));
   }
 
   /** Loads and registers the custom element defined on the `WithCustomElement` module factory. */

aio/src/app/custom-elements/toc/toc.component.ts

@@ -1,5 +1,5 @@
 import { AfterViewInit, Component, ElementRef, OnDestroy, OnInit, QueryList, ViewChildren } from '@angular/core';
-import { asapScheduler as asap, combineLatest, Subject } from 'rxjs';
+import { asapScheduler, combineLatest, Subject } from 'rxjs';
 import { startWith, subscribeOn, takeUntil } from 'rxjs/operators';
 
 import { ScrollService } from 'app/shared/scroll.service';
@@ -52,7 +52,7 @@ export class TocComponent implements OnInit, AfterViewInit, OnDestroy {
       // We use the `asap` scheduler because updates to `activeItemIndex` are triggered by DOM changes,
       // which, in turn, are caused by the rendering that happened due to a ChangeDetection.
       // Without asap, we would be updating the model while still in a ChangeDetection handler, which is disallowed by Angular.
-      combineLatest(this.tocService.activeItemIndex.pipe(subscribeOn(asap)), this.items.changes.pipe(startWith(this.items)))
+      combineLatest(this.tocService.activeItemIndex.pipe(subscribeOn(asapScheduler)), this.items.changes.pipe(startWith(this.items)))
           .pipe(takeUntil(this.onDestroy))
           .subscribe(([index, items]) => {
             this.activeIndex = index;