address feedback

Author: mmalerba

src/material-experimental/mdc-list/list-base.ts

@@ -6,24 +6,29 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {AfterContentInit, ElementRef, NgZone, OnDestroy, QueryList} from '@angular/core';
+import {ElementRef, NgZone, OnDestroy, QueryList} from '@angular/core';
 import {setLines} from '@angular/material/core';
 import {Subscription} from 'rxjs';
-import {startWith} from 'rxjs/operators';
 
 export class MatListBase {}
 
-export class MatListItemBase implements AfterContentInit, OnDestroy {
+export class MatListItemBase implements OnDestroy {
   lines: QueryList<ElementRef<Element>>;
 
   private _subscriptions = new Subscription();
 
-  constructor(protected _element: ElementRef, protected _ngZone: NgZone) {}
+  constructor(protected _element: ElementRef, protected _ngZone: NgZone) {
+    this._monitorLines();
+  }
 
-  ngAfterContentInit() {
+  /**
+   * Subscribes to changes in `MatLine` content children and annotates them appropriately when they
+   * change.
+   */
+  private _monitorLines() {
     this._ngZone.runOutsideAngular(() => {
-      this._subscriptions.add(this.lines.changes.pipe(startWith(this.lines))
-          .subscribe((lines: QueryList<ElementRef<Element>>) => {
+      this._subscriptions.add(
+          this.lines.changes.subscribe((lines: QueryList<ElementRef<Element>>) => {
             lines.forEach((line: ElementRef<Element>, index: number) => {
               line.nativeElement.classList.toggle('mdc-list-item__primary-text', index === 0);
               line.nativeElement.classList.toggle('mdc-list-item__secondary-text', index !== 0);