feat(AgmMap): Add tilesloaded event to AgmMap (#1706)

fixes: #1701

packages/core/directives/map.ts

@@ -358,6 +358,11 @@ export class AgmMap implements OnChanges, OnInit, OnDestroy {
    */
   @Output() mapReady: EventEmitter<any> = new EventEmitter<any>();
 
+  /**
+   * This event is fired when the visible tiles have finished loading.
+   */
+  @Output() tilesLoaded: EventEmitter<void> = new EventEmitter<void>();
+
   constructor(private _elem: ElementRef, private _mapsWrapper: GoogleMapsAPIWrapper, protected _fitBoundsService: FitBoundsService, private _zone: NgZone) {
   }
 
@@ -413,6 +418,7 @@ export class AgmMap implements OnChanges, OnInit, OnDestroy {
     this._handleMapMouseEvents();
     this._handleBoundsChange();
     this._handleMapTypeIdChange();
+    this._handleTilesLoadedEvent();
     this._handleIdleEvent();
   }
 
@@ -577,6 +583,13 @@ export class AgmMap implements OnChanges, OnInit, OnDestroy {
     this._observableSubscriptions.push(s);
   }
 
+  private _handleTilesLoadedEvent() {
+    const s = this._mapsWrapper.subscribeToMapEvent<void>('tilesloaded').subscribe(
+      () => this.tilesLoaded.emit(void 0)
+    );
+    this._observableSubscriptions.push(s);
+  }
+
   private _handleMapMouseEvents() {
     interface Emitter {
       emit(value: any): void;