message: fix(platform-browser): fix destroy hammer manager when off
  PR Close
diff: @@ -71,6 +71,7 @@ export const HAMMER_LOADER = new InjectionToken<HammerLoader>('HammerLoader');
  export interface HammerInstance {
  on(eventName: string, callback?: Function): void;
  off(eventName: string, callback?: Function): void;
  + destroy?(): void;
  }
  /**
  @@ -214,7 +215,13 @@ export class HammerGesturesPlugin extends EventManagerPlugin {
  zone.runGuarded(function() { handler(eventObj); });
  };
  mc.on(eventName, callback);
  - return () => mc.off(eventName, callback);
  + return () => {
  + mc.off(eventName, callback);
  + // destroy mc to prevent memory leak
  + if (typeof mc.destroy === 'function') {
  + mc.destroy();
  + }
  + };
  });
  }
  