Revert "[web] Accepts assetBase through JS config. (#40615)" (#40670)

This reverts commit f7d2571.

This commit is causing problems with new lint rules:

```
   info - test/engine/assets_test.dart:5:1 - This annotation must be attached to a library directive. Try attaching library annotations to library directives. - library_annotations
```

Author: ditman

lib/web_ui/lib/src/engine/assets.dart

@@ -24,48 +24,26 @@ const Map<String, String> testFontUrls = <String, String>{
 
 /// This class downloads assets over the network.
 ///
-/// Assets are resolved relative to [assetsDir] inside the absolute base
-/// specified by [assetBase] (optional).
-///
-/// By default, URLs are relative to the `<base>` of the current website.
+/// The assets are resolved relative to [assetsDir] inside the directory
+/// containing the currently executing JS script.
 class AssetManager {
-  /// Initializes [AssetManager] with paths.
-  AssetManager({
-    this.assetsDir = _defaultAssetsDir,
-    String? assetBase,
-  })  : assert(
-          assetBase == null || assetBase.endsWith('/'),
-          '`assetBase` must end with a `/` character.',
-        ),
-        _assetBase = assetBase;
+  /// Initializes [AssetManager] with path to assets relative to baseUrl.
+  const AssetManager({this.assetsDir = _defaultAssetsDir});
 
   static const String _defaultAssetsDir = 'assets';
 
   /// The directory containing the assets.
   final String assetsDir;
 
-  /// The absolute base URL for assets.
-  String? _assetBase;
-
-  // Cache a value for `_assetBase` so we don't hit the DOM multiple times.
-  String get _baseUrl => _assetBase ??= _deprecatedAssetBase ?? '';
-
-  // Retrieves the `assetBase` value from the DOM.
-  //
-  // This warns the user and points them to the new initializeEngine style.
-  String? get _deprecatedAssetBase {
-    final DomHTMLMetaElement? meta = domWindow.document
-        .querySelector('meta[name=assetBase]') as DomHTMLMetaElement?;
-
-    final String? fallbackBaseUrl = meta?.content;
-
-    if (fallbackBaseUrl != null) {
-      // Warn users that they're using a deprecated configuration style...
-      domWindow.console.warn('The `assetBase` meta tag is now deprecated.\n'
-          'Use engineInitializer.initializeEngine(config) instead.\n'
-          'See: https://docs.flutter.dev/development/platform-integration/web/initialization');
-    }
-    return fallbackBaseUrl;
+  String? get _baseUrl {
+    return domWindow.document
+        .querySelectorAll('meta')
+        .where((DomElement domNode) => domInstanceOfString(domNode,
+                'HTMLMetaElement'))
+        .map((DomElement domNode) => domNode as DomHTMLMetaElement)
+        .firstWhereOrNull(
+            (DomHTMLMetaElement element) => element.name == 'assetBase')
+        ?.content;
   }
 
   /// Returns the URL to load the asset from, given the asset key.
@@ -89,7 +67,7 @@ class AssetManager {
     if (Uri.parse(asset).hasScheme) {
       return Uri.encodeFull(asset);
     }
-    return Uri.encodeFull('$_baseUrl$assetsDir/$asset');
+    return Uri.encodeFull('${_baseUrl ?? ''}$assetsDir/$asset');
   }
 
   /// Loads an asset and returns the server response.
@@ -112,7 +90,7 @@ class AssetManager {
 }
 
 /// An asset manager that gives fake empty responses for assets.
-class WebOnlyMockAssetManager extends AssetManager {
+class WebOnlyMockAssetManager implements AssetManager {
   /// Mock asset directory relative to base url.
   String defaultAssetsDir = '';
 
@@ -135,6 +113,9 @@ class WebOnlyMockAssetManager extends AssetManager {
   @override
   String get assetsDir => defaultAssetsDir;
 
+  @override
+  String get _baseUrl => '';
+
   @override
   String getAssetUrl(String asset) => asset;
 
@@ -146,7 +127,7 @@ class WebOnlyMockAssetManager extends AssetManager {
         status: 200,
         payload: MockHttpFetchPayload(
           byteBuffer: _toByteData(utf8.encode(defaultAssetManifest)).buffer,
-        ),
+        )
       );
     }
     if (asset == getAssetUrl('FontManifest.json')) {
@@ -155,7 +136,7 @@ class WebOnlyMockAssetManager extends AssetManager {
         status: 200,
         payload: MockHttpFetchPayload(
           byteBuffer: _toByteData(utf8.encode(defaultFontManifest)).buffer,
-        ),
+        )
       );
     }
 

lib/web_ui/lib/src/engine/configuration.dart

@@ -153,32 +153,6 @@ class FlutterConfiguration {
   // runtime. Runtime-supplied values take precedence over environment
   // variables.
 
-  /// The absolute base URL of the location of the `assets` directory of the app.
-  ///
-  /// This value is useful when Flutter web assets are deployed to a separate
-  /// domain (or subdirectory) from which the index.html is served, for example:
-  ///
-  /// * Application: https://www.my-app.com/
-  /// * Flutter Assets: https://cdn.example.com/my-app/build-hash/assets/
-  ///
-  /// The `assetBase` value would be set to:
-  ///
-  /// * `'https://cdn.example.com/my-app/build-hash/'`
-  ///
-  /// It is also useful in the case that a Flutter web application is embedded
-  /// into another web app, in a way that the `<base>` tag of the index.html
-  /// cannot be set (because it'd break the host app), for example:
-  ///
-  /// * Application: https://www.my-app.com/
-  /// * Flutter Assets: https://www.my-app.com/static/companion/flutter/assets/
-  ///
-  /// The `assetBase` would be set to:
-  ///
-  /// * `'/static/companion/flutter/'`
-  ///
-  /// Do not confuse this configuration value with [canvasKitBaseUrl].
-  String? get assetBase => _configuration?.assetBase;
-
   /// The base URL to use when downloading the CanvasKit script and associated
   /// wasm.
   ///
@@ -288,10 +262,6 @@ external JsFlutterConfiguration? get _jsConfiguration;
 class JsFlutterConfiguration {}
 
 extension JsFlutterConfigurationExtension on JsFlutterConfiguration {
-  @JS('assetBase')
-  external JSString? get _assetBase;
-  String? get assetBase => _assetBase?.toDart;
-
   @JS('canvasKitBaseUrl')
   external JSString? get _canvasKitBaseUrl;
   String? get canvasKitBaseUrl => _canvasKitBaseUrl?.toDart;

lib/web_ui/lib/src/engine/initialization.dart

@@ -211,7 +211,7 @@ Future<void> initializeEngineServices({
     }
   };
 
-  assetManager ??= AssetManager(assetBase: configuration.assetBase);
+  assetManager ??= const AssetManager();
   _setAssetManager(assetManager);
 
   Future<void> initializeRendererCallback () async => renderer.initialize();