build: bootstrap app after theme is loaded

Usually themes are loaded as global styles which are blocking. This allows us to assume that by the time to app is bootstrapped, the theme should have loaded. Our own demo app doesn't work this way, because we're inserting the theme inside the main entrypoint, because we need to determine whether to insert an M2 or M3 theme. This prevented us from properly testing the theme loaded warning.

These changes switch to bootstrapping the app after the theme has loaded.

(cherry picked from commit 1214b4e)

src/dev-app/main.ts

@@ -9,7 +9,6 @@
 // Load `$localize` for examples using it.
 import '@angular/localize/init';
 
-import {HttpClientModule} from '@angular/common/http';
 import {
   importProvidersFrom,
   provideZoneChangeDetection,
@@ -36,23 +35,28 @@ const theme = document.createElement('link');
 theme.href = cachedAppState.m3Enabled ? 'theme-m3.css' : 'theme.css';
 theme.id = 'theme-styles';
 theme.rel = 'stylesheet';
+
+// Bootstrap the app after the theme has loaded so we can properly test the
+// theme loaded checks. This also avoids a flicker if it takes too long to load.
+theme.addEventListener('load', bootstrap, {once: true});
 document.head.appendChild(theme);
 
-bootstrapApplication(DevApp, {
-  providers: [
-    importProvidersFrom(
-      BrowserAnimationsModule.withConfig({
-        disableAnimations: !cachedAppState.animations,
-      }),
-      RouterModule.forRoot(DEV_APP_ROUTES),
-      HttpClientModule,
-    ),
-    provideNativeDateAdapter(),
-    {provide: OverlayContainer, useClass: FullscreenOverlayContainer},
-    {provide: MAT_RIPPLE_GLOBAL_OPTIONS, useExisting: DevAppRippleOptions},
-    {provide: Directionality, useClass: DevAppDirectionality},
-    cachedAppState.zoneless
-      ? provideExperimentalZonelessChangeDetection()
-      : provideZoneChangeDetection({eventCoalescing: true, runCoalescing: true}),
-  ],
-});
+function bootstrap(): void {
+  bootstrapApplication(DevApp, {
+    providers: [
+      importProvidersFrom(
+        BrowserAnimationsModule.withConfig({
+          disableAnimations: !cachedAppState.animations,
+        }),
+        RouterModule.forRoot(DEV_APP_ROUTES),
+      ),
+      provideNativeDateAdapter(),
+      {provide: OverlayContainer, useClass: FullscreenOverlayContainer},
+      {provide: MAT_RIPPLE_GLOBAL_OPTIONS, useExisting: DevAppRippleOptions},
+      {provide: Directionality, useClass: DevAppDirectionality},
+      cachedAppState.zoneless
+        ? provideExperimentalZonelessChangeDetection()
+        : provideZoneChangeDetection({eventCoalescing: true, runCoalescing: true}),
+    ],
+  });
+}