fix(animations): ensure all child elements are rendered before running animations

Closes #9402
Closes #9775

tools/public_api_guard/core/index.d.ts

@@ -67,6 +67,8 @@ export declare abstract class AnimationPlayer {
     abstract destroy(): void;
     abstract finish(): void;
     abstract getPosition(): number;
+    abstract hasStarted(): boolean;
+    abstract init(): void;
     abstract onDone(fn: Function): void;
     abstract pause(): void;
     abstract play(): void;