[Modal] allow user's define injector

[tieppt]

What problem does this feature solve?

When using modal, you're using ViewContainerRef from constructor injection to create child injector, which lead to an issue: the component we want to dynamic rendering (may request service provided by any level of injector tree), can not get right services.

Stackblitz: https://stackblitz.com/edit/angular-jdeqhr?file=src/app/app.component.ts

What does the proposed API look like?

User can send an instance of ViewContainerRef (this is optional) as Material Dialog approach.

private _createInjector<T>(
      config: MatDialogConfig,
      dialogRef: MatDialogRef<T>,
      dialogContainer: MatDialogContainer): PortalInjector {

    const userInjector = config && config.viewContainerRef && config.viewContainerRef.injector;

    // The MatDialogContainer is injected in the portal as the MatDialogContainer and the dialog's
    // content are created out of the same ViewContainerRef and as such, are siblings for injector
    // purposes. To allow the hierarchy that is expected, the MatDialogContainer is explicitly
    // added to the injection tokens.
    const injectionTokens = new WeakMap<any, any>([
      [MatDialogContainer, dialogContainer],
      [MAT_DIALOG_DATA, config.data],
      [MatDialogRef, dialogRef]
    ]);

    if (config.direction &&
        (!userInjector || !userInjector.get<Directionality | null>(Directionality, null))) {
      injectionTokens.set(Directionality, {
        value: config.direction,
        change: observableOf()
      });
    }

    return new PortalInjector(userInjector || this._injector, injectionTokens);
  }

[marct83]

Did this go into V10? I'm still seeing my modal components not inheriting Providers from parent component.