docs: add api stability indicators for @angular/common

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

@@ -45,6 +45,8 @@ import {UrlChangeListener, PlatformLocation} from './platform_location';
  *   provide(LocationStrategy, {useClass: HashLocationStrategy})
  * ]);
  * ```
+ *
+ * @stable
  */
 @Injectable()
 export class HashLocationStrategy extends LocationStrategy {

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

@@ -42,6 +42,8 @@ import {LocationStrategy} from './location_strategy';
  *
  * bootstrap(AppCmp, [ROUTER_PROVIDERS]);
  * ```
+ *
+ * @stable
  */
 @Injectable()
 export class Location {

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

@@ -16,6 +16,8 @@ import {UrlChangeListener} from './platform_location';
  * `http://example.com/foo` as an equivalent URL.
  *
  * See these two classes for more.
+ *
+ * @stable
  */
 export abstract class LocationStrategy {
   abstract path(): string;
@@ -57,5 +59,6 @@ export abstract class LocationStrategy {
  *   provide(APP_BASE_HREF, {useValue: '/my/app'})
  * ]);
  * ```
+ * @stable
  */
 export const APP_BASE_HREF: OpaqueToken = /*@ts2dart_const*/ new OpaqueToken('appBaseHref');

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

@@ -53,6 +53,8 @@ import {Location} from './location';
  *   provide(APP_BASE_HREF, {useValue: '/my/app'})
  * ]);
  * ```
+ *
+ * @stable
  */
 @Injectable()
 export class PathLocationStrategy extends LocationStrategy {

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

@@ -21,6 +21,8 @@
  * {@link Location} / {@link LocationStrategy} and DOM apis flow through the `PlatformLocation`
  * class
  * they are all platform independent.
+ *
+ * @stable
  */
 export abstract class PlatformLocation {
   abstract getBaseHrefFromDOM(): string;
@@ -42,6 +44,8 @@ export abstract class PlatformLocation {
 
 /**
  * A serializable version of the event from onPopState or onHashChange
+ *
+ * @stable
  */
 export interface UrlChangeEvent { type: string; }