chore: stop importing symbols from zone-types.d.ts

Author: mmalerba

src/cdk/testing/testbed/task-state-zone-interceptor.ts

@@ -8,7 +8,6 @@
 
 import {BehaviorSubject, Observable} from 'rxjs';
 import {ProxyZone, ProxyZoneStatic} from './proxy-zone-types';
-import {HasTaskState, Zone, ZoneDelegate} from './zone-types';
 
 /** Current state of the intercepted zone. */
 export interface TaskState {

src/cdk/testing/testbed/zone-types.d.ts

@@ -14,11 +14,9 @@
  * here and use these for our interceptor logic.
  */
 
-declare global {
-  // tslint:disable-next-line:variable-name
-  const Zone: {current: any}|undefined;
+declare interface Zone {
+  current: any;
 }
-
-export type Zone = Object;
-export type ZoneDelegate = Object;
-export type HasTaskState = {microTask: boolean, macroTask: boolean};
+declare const Zone: Zone | undefined;
+declare type ZoneDelegate = Object;
+declare type HasTaskState = {microTask: boolean, macroTask: boolean};