fix(material/dialog): MatDialog: change member _dialog (cdk) from private to protected (#28019) (#28020)

Having customized MatDialog allow to have customized cdk/dialog inside of it.

(cherry picked from commit 238e978)

Author: dolezaljan

src/material/dialog/dialog.ts

@@ -82,7 +82,7 @@ export class MatDialog implements OnDestroy {
   private readonly _openDialogsAtThisLevel: MatDialogRef<any>[] = [];
   private readonly _afterAllClosedAtThisLevel = new Subject<void>();
   private readonly _afterOpenedAtThisLevel = new Subject<MatDialogRef<any>>();
-  private _dialog: Dialog;
+  protected _dialog: Dialog;
   protected dialogConfigClass = MatDialogConfig;
 
   private readonly _dialogRefConstructor: Type<MatDialogRef<any>>;

tools/public_api_guard/material/dialog.md

@@ -10,6 +10,7 @@ import { ComponentFactoryResolver } from '@angular/core';
 import { ComponentPortal } from '@angular/cdk/portal';
 import { ComponentRef } from '@angular/core';
 import { ComponentType } from '@angular/cdk/overlay';
+import { Dialog } from '@angular/cdk/dialog';
 import { DialogRef } from '@angular/cdk/dialog';
 import { Direction } from '@angular/cdk/bidi';
 import { ElementRef } from '@angular/core';
@@ -94,6 +95,8 @@ export class MatDialog implements OnDestroy {
     get afterOpened(): Subject<MatDialogRef<any>>;
     closeAll(): void;
     // (undocumented)
+    protected _dialog: Dialog;
+    // (undocumented)
     protected dialogConfigClass: typeof MatDialogConfig;
     getDialogById(id: string): MatDialogRef<any> | undefined;
     // (undocumented)