refactor: replace asObservable usages (#20165)

As discussed, replaces usages of the `asObservable` with a cast to `Observable` since the method is a little pointless, because people can easily get around it if they really want to.

Also cleans up a few getters that were returning observables.

Author: crisbeto

src/cdk-experimental/column-resize/column-resize-notifier.ts

@@ -56,7 +56,7 @@ export class ColumnResizeNotifierSource {
 @Injectable()
 export class ColumnResizeNotifier {
   /** Emits whenever a column is resized. */
-  readonly resizeCompleted: Observable<ColumnSize> = this._source.resizeCompleted.asObservable();
+  readonly resizeCompleted: Observable<ColumnSize> = this._source.resizeCompleted;
 
   constructor(private readonly _source: ColumnResizeNotifierSource) {}
 

src/cdk-experimental/dialog/dialog-ref.ts

@@ -133,12 +133,12 @@ export class DialogRef<T, R = any> {
 
   /** Gets an observable that emits when dialog begins opening. */
   beforeOpened(): Observable<void> {
-    return this._containerInstance._beforeEnter.asObservable();
+    return this._containerInstance._beforeEnter;
   }
 
   /** Gets an observable that emits when dialog is finished opening. */
   afterOpened(): Observable<void> {
-    return this._containerInstance._afterEnter.asObservable();
+    return this._containerInstance._afterEnter;
   }
 
   /** Gets an observable that emits when dialog begins closing. */

src/cdk-experimental/popover-edit/edit-ref.ts

@@ -21,11 +21,11 @@ import {EditEventDispatcher} from './edit-event-dispatcher';
 export class EditRef<FormValue> implements OnDestroy {
   /** Emits the final value of this edit instance before closing. */
   private readonly _finalValueSubject = new Subject<FormValue>();
-  readonly finalValue: Observable<FormValue> = this._finalValueSubject.asObservable();
+  readonly finalValue: Observable<FormValue> = this._finalValueSubject;
 
   /** Emits when the user tabs out of this edit lens before closing. */
   private readonly _blurredSubject = new Subject<void>();
-  readonly blurred: Observable<void> = this._blurredSubject.asObservable();
+  readonly blurred: Observable<void> = this._blurredSubject;
 
   /** The value to set the form back to on revert. */
   private _revertFormValue: FormValue;

src/cdk-experimental/popover-edit/focus-escape-notifier.ts

@@ -46,7 +46,7 @@ export class FocusEscapeNotifier extends FocusTrap {
   }
 
   escapes(): Observable<FocusEscapeNotifierDirection> {
-    return this._escapeSubject.asObservable();
+    return this._escapeSubject;
   }
 }
 

src/cdk-experimental/popover-edit/popover-edit.spec.ts

@@ -253,7 +253,7 @@ class ElementDataSource extends DataSource<PeriodicElement> {
 
   /** Connect function called by the table to retrieve one stream containing the data to render. */
   connect() {
-    return this.data.asObservable();
+    return this.data;
   }
 
   disconnect() {}

src/cdk/a11y/focus-monitor/focus-monitor.ts

@@ -247,7 +247,7 @@ export class FocusMonitor implements OnDestroy {
         cachedInfo.checkChildren = true;
       }
 
-      return cachedInfo.subject.asObservable();
+      return cachedInfo.subject;
     }
 
     // Create monitored element info.
@@ -259,7 +259,7 @@ export class FocusMonitor implements OnDestroy {
     this._elementInfo.set(nativeElement, info);
     this._registerGlobalListeners(info);
 
-    return info.subject.asObservable();
+    return info.subject;
   }
 
   /**

src/cdk/a11y/focus-trap/focus-trap.ts

@@ -341,7 +341,7 @@ export class FocusTrap {
     if (this._ngZone.isStable) {
       fn();
     } else {
-      this._ngZone.onStable.asObservable().pipe(take(1)).subscribe(fn);
+      this._ngZone.onStable.pipe(take(1)).subscribe(fn);
     }
   }
 }

src/cdk/drag-drop/directives/drag.spec.ts

@@ -2407,7 +2407,7 @@ describe('CdkDrag', () => {
       const itemInstance = fixture.componentInstance.dragItems.toArray()[1];
       const item = itemInstance.element.nativeElement;
       const spy = jasmine.createSpy('dropped spy');
-      const subscription = itemInstance.dropped.asObservable().subscribe(spy);
+      const subscription = itemInstance.dropped.subscribe(spy);
 
       // Do an initial drag and drop sequence.
       dragElementViaMouse(fixture, item, 50, 50);

src/cdk/drag-drop/directives/drag.ts

@@ -251,7 +251,7 @@ export class CdkDrag<T = any> implements AfterViewInit, OnChanges, OnDestroy {
     // element to be in the proper place in the DOM. This is mostly relevant
     // for draggable elements inside portals since they get stamped out in
     // their original DOM position and then they get transferred to the portal.
-    this._ngZone.onStable.asObservable()
+    this._ngZone.onStable
       .pipe(take(1), takeUntil(this._destroyed))
       .subscribe(() => {
         this._updateRootElement();

src/cdk/drag-drop/drag-ref.ts

@@ -292,7 +292,7 @@ export class DragRef<T = any> {
     event: MouseEvent | TouchEvent;
     distance: Point;
     delta: {x: -1 | 0 | 1, y: -1 | 0 | 1};
-  }> = this._moveEvents.asObservable();
+  }> = this._moveEvents;
 
   /** Arbitrary data that can be attached to the drag item. */
   data: T;