[web] Remove --web-renderer=auto and default to canvaskit

lib/web_ui/dev/steps/compile_bundle_step.dart

@@ -215,10 +215,6 @@ class Dart2JSCompiler extends TestCompiler {
       '--disable-inlining',
       '--enable-asserts',
 
-      // We do not want to auto-select a renderer in tests. As of today, tests
-      // are designed to run in one specific mode. So instead, we specify the
-      // renderer explicitly.
-      '-DFLUTTER_WEB_AUTO_DETECT=false',
       '-DFLUTTER_WEB_USE_SKIA=${renderer == Renderer.canvaskit}',
       '-DFLUTTER_WEB_USE_SKWASM=${renderer == Renderer.skwasm}',
 
@@ -279,10 +275,6 @@ class Dart2WasmCompiler extends TestCompiler {
       '--dart-sdk=${environment.dartSdkDir.path}',
       '--enable-asserts',
 
-      // We do not want to auto-select a renderer in tests. As of today, tests
-      // are designed to run in one specific mode. So instead, we specify the
-      // renderer explicitly.
-      '-DFLUTTER_WEB_AUTO_DETECT=false',
       '-DFLUTTER_WEB_USE_SKIA=${renderer == Renderer.canvaskit}',
       '-DFLUTTER_WEB_USE_SKWASM=${renderer == Renderer.skwasm}',
 

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

@@ -165,13 +165,6 @@ class FlutterConfiguration {
   // runtime. They must be static constants for the compiler to remove dead code
   // effectively.
 
-  /// Auto detect which rendering backend to use.
-  ///
-  /// Using flutter tools option "--web-render=auto" or not specifying one
-  /// would set the value to true. Otherwise, it would be false.
-  static const bool flutterWebAutoDetect =
-      bool.fromEnvironment('FLUTTER_WEB_AUTO_DETECT', defaultValue: true);
-
   static const bool flutterWebUseSkwasm =
       bool.fromEnvironment('FLUTTER_WEB_USE_SKWASM');
 

lib/web_ui/lib/src/engine/renderer.dart

@@ -23,22 +23,11 @@ abstract class Renderer {
   factory Renderer._internal() {
     if (FlutterConfiguration.flutterWebUseSkwasm) {
       return SkwasmRenderer();
-    } else {
-      bool useCanvasKit;
-      if (FlutterConfiguration.flutterWebAutoDetect) {
-        if (configuration.requestedRendererType != null) {
-          useCanvasKit = configuration.requestedRendererType == 'canvaskit';
-        } else {
-          // If requestedRendererType is not specified, use CanvasKit for desktop and
-          // html for mobile.
-          useCanvasKit = isDesktop;
-        }
-      } else {
-        useCanvasKit = FlutterConfiguration.useSkia;
-      }
-
-      return useCanvasKit ? CanvasKitRenderer() : HtmlRenderer();
     }
+    if (FlutterConfiguration.useSkia) {
+      return CanvasKitRenderer();
+    }
+    return HtmlRenderer();
   }
 
   String get rendererTag;

lib/web_ui/lib/src/engine/view_embedder/global_html_attributes.dart

@@ -25,7 +25,6 @@ class GlobalHtmlAttributes {
 
   void applyAttributes({
     required int viewId,
-    required bool autoDetectRenderer,
     required String rendererTag,
     required String buildMode,
   }) {
@@ -39,12 +38,7 @@ class GlobalHtmlAttributes {
     //     document.querySelector('flutter-view[flt-view-id="$viewId"]')
     rootElement.setAttribute(flutterViewIdAttributeName, viewId);
 
-    // How was the current renderer selected?
-    final String rendererSelection = autoDetectRenderer
-        ? 'auto-selected'
-        : 'requested explicitly';
-
-    hostElement.setAttribute('flt-renderer', '$rendererTag ($rendererSelection)');
+    hostElement.setAttribute('flt-renderer', rendererTag);
     hostElement.setAttribute('flt-build-mode', buildMode);
     // TODO(mdebbar): Disable spellcheck until changes in the framework and
     // engine are complete.

lib/web_ui/lib/src/engine/window.dart

@@ -11,7 +11,6 @@ import 'package:ui/ui_web/src/ui_web.dart' as ui_web;
 
 import '../engine.dart' show DimensionsProvider, registerHotRestartListener, renderer;
 import 'browser_detection.dart';
-import 'configuration.dart';
 import 'display.dart';
 import 'dom.dart';
 import 'initialization.dart';
@@ -75,7 +74,6 @@ base class EngineFlutterView implements ui.FlutterView {
     _resizeSubscription = onResize.listen(_didResize);
     _globalHtmlAttributes.applyAttributes(
       viewId: viewId,
-      autoDetectRenderer: FlutterConfiguration.flutterWebAutoDetect,
       rendererTag: renderer.rendererTag,
       buildMode: buildMode,
     );

lib/web_ui/test/engine/view_embedder/global_html_attributes_test.dart

@@ -22,25 +22,23 @@ void doTests() {
 
       globalHtmlAttributes.applyAttributes(
         viewId: 123,
-        autoDetectRenderer: true,
         rendererTag: 'canvaskit',
         buildMode: 'release',
       );
 
       expect(rootElement.getAttribute('flt-view-id'), '123');
-      expect(hostElement.getAttribute('flt-renderer'), 'canvaskit (auto-selected)');
+      expect(hostElement.getAttribute('flt-renderer'), 'canvaskit');
       expect(hostElement.getAttribute('flt-build-mode'), 'release');
       expect(hostElement.getAttribute('spellcheck'), 'false');
 
       globalHtmlAttributes.applyAttributes(
         viewId: 456,
-        autoDetectRenderer: false,
         rendererTag: 'html',
         buildMode: 'debug',
       );
 
       expect(rootElement.getAttribute('flt-view-id'), '456');
-      expect(hostElement.getAttribute('flt-renderer'), 'html (requested explicitly)');
+      expect(hostElement.getAttribute('flt-renderer'), 'html');
       expect(hostElement.getAttribute('flt-build-mode'), 'debug');
       expect(hostElement.getAttribute('spellcheck'), 'false');
     });

lib/web_ui/test/engine/window_test.dart

@@ -467,7 +467,7 @@ Future<void> testMain() async {
     final DomElement host = createDomHTMLDivElement();
     final EngineFlutterView view = EngineFlutterView(dispatcher, host);
 
-    expect(host.getAttribute('flt-renderer'), 'html (requested explicitly)');
+    expect(host.getAttribute('flt-renderer'), 'html');
     expect(host.getAttribute('flt-build-mode'), 'debug');
 
     view.dispose();