fix(common): add PopStateEvent interface

Closes #13378

modules/@angular/common/src/location/location.ts

@@ -10,6 +10,12 @@ import {EventEmitter, Injectable} from '@angular/core';
 
 import {LocationStrategy} from './location_strategy';
 
+/** @experimental */
+export interface PopStateEvent {
+  pop?: boolean;
+  type?: string;
+  url?: string;
+}
 
 /**
  * `Location` is a service that applications can use to interact with a browser's URL.
@@ -133,7 +139,7 @@ export class Location {
    * Subscribe to the platform's `popState` events.
    */
   subscribe(
-      onNext: (value: any) => void, onThrow: (exception: any) => void = null,
+      onNext: (value: PopStateEvent) => void, onThrow: (exception: any) => void = null,
       onReturn: () => void = null): Object {
     return this._subject.subscribe({next: onNext, error: onThrow, complete: onReturn});
   }

tools/public_api_guard/common/index.d.ts

@@ -74,7 +74,7 @@ export declare class Location {
     path(includeHash?: boolean): string;
     prepareExternalUrl(url: string): string;
     replaceState(path: string, query?: string): void;
-    subscribe(onNext: (value: any) => void, onThrow?: (exception: any) => void, onReturn?: () => void): Object;
+    subscribe(onNext: (value: PopStateEvent) => void, onThrow?: (exception: any) => void, onReturn?: () => void): Object;
     static joinWithSlash(start: string, end: string): string;
     static normalizeQueryParams(params: string): string;
     static stripTrailingSlash(url: string): string;
@@ -220,6 +220,13 @@ export declare abstract class PlatformLocation {
     abstract replaceState(state: any, title: string, url: string): void;
 }
 
+/** @experimental */
+export interface PopStateEvent {
+    pop?: boolean;
+    type?: string;
+    url?: string;
+}
+
 /** @stable */
 export declare class SlicePipe implements PipeTransform {
     transform(value: any, start: number, end?: number): any;