chore(internal API): introduce an internal API for ngtools. (#13415)

modules/@angular/compiler-cli/integrationtest/ngtools_src/lazy.module.ts

@@ -0,0 +1,23 @@
+import {NgModule, Component} from '@angular/core';
+import {RouterModule} from '@angular/router';
+
+@Component({
+  selector: 'lazy-comp',
+  template: 'lazy!'
+})
+export class LazyComponent {}
+
+@NgModule({
+  imports: [
+    RouterModule.forChild([
+     {path: '', component: LazyComponent, pathMatch: 'full'},
+     {path: 'feature', loadChildren: './feature/feature.module#FeatureModule'},
+     {path: 'lazy-feature', loadChildren: './feature/lazy-feature.module#LazyFeatureModule'}
+    ])
+  ],
+  declarations: [LazyComponent]
+})
+export class LazyModule {
+}
+
+export class SecondModule {}