fix(common): temporarily re-export and deprecate XhrFactory

The `XhrFactory` still needs to be available from `@angular/common/http`
for some libraries that were built prior to 12.0.0, otherwise they cannot
be used in application built post-12.0.0.

goldens/public-api/common/http/http.d.ts

@@ -1930,7 +1930,7 @@ export declare interface HttpUserEvent<T> {
 }
 
 export declare class HttpXhrBackend implements HttpBackend {
-    constructor(xhrFactory: XhrFactory);
+    constructor(xhrFactory: XhrFactory_2);
     handle(req: HttpRequest<any>): Observable<HttpEvent<any>>;
 }
 
@@ -1947,3 +1947,6 @@ export declare class JsonpInterceptor {
     constructor(jsonp: JsonpClientBackend);
     intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>>;
 }
+
+/** @deprecated */
+export declare type XhrFactory = XhrFactory_2;

packages/common/http/public_api.ts

@@ -6,6 +6,25 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {XhrFactory as XhrFactory_fromAngularCommon} from '@angular/common';
+
+/**
+ * A wrapper around the `XMLHttpRequest` constructor.
+ * @publicApi
+ * @deprecated
+ * `XhrFactory`` has been moved to `@angular/common`, please update your code to import it from
+ * there.
+ */
+export type XhrFactory = XhrFactory_fromAngularCommon;
+/**
+ * A wrapper around the `XMLHttpRequest` constructor.
+ * @publicApi
+ * @deprecated
+ * `XhrFactory`` has been moved to `@angular/common`, please update your code to import it from
+ * there.
+ */
+export const XhrFactory = XhrFactory_fromAngularCommon;
+
 export {HttpBackend, HttpHandler} from './src/backend';
 export {HttpClient} from './src/client';
 export {HttpContext, HttpContextToken} from './src/context';

packages/misc/angular-in-memory-web-api/src/in-memory-web-api-module.ts

@@ -6,8 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {XhrFactory} from '@angular/common';
-import {HttpBackend} from '@angular/common/http';
+import {HttpBackend, XhrFactory} from '@angular/common/http';
 import {ModuleWithProviders, NgModule, Type} from '@angular/core';
 
 import {httpClientInMemBackendServiceFactory} from './http-client-in-memory-web-api-module';