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

modules/@angular/compiler-cli/integrationtest/ngtools_src/feature2/default.module.ts

@@ -0,0 +1,20 @@
+import {NgModule, Component} from '@angular/core';
+import {RouterModule} from '@angular/router';
+
+@Component({
+  selector: 'feature-component',
+  template: 'foo.html'
+})
+export class FeatureComponent {}
+
+@NgModule({
+  declarations: [
+    FeatureComponent
+  ],
+  imports: [
+    RouterModule.forChild([
+      { path: '', component: FeatureComponent },
+    ])
+  ]
+})
+export default class DefaultModule {}