Add feature flag scaffolding to support experiments restricted to a specific Flutter channel (#9440)

Author: elliette

packages/devtools_app/lib/src/app.dart

@@ -86,7 +86,7 @@ class DevToolsApp extends StatefulWidget {
 /// flutter route parameters.
 class DevToolsAppState extends State<DevToolsApp> with AutoDisposeMixin {
   List<Screen> get _screens {
-    if (FeatureFlags.devToolsExtensions) {
+    if (FeatureFlags.devToolsExtensions.isEnabled) {
       // TODO(https://github.com/flutter/devtools/issues/6273): stop special
       // casing the package:provider extension.
       final containsProviderExtension = extensionService
@@ -177,7 +177,7 @@ class DevToolsAppState extends State<DevToolsApp> with AutoDisposeMixin {
       });
     }
 
-    if (FeatureFlags.devToolsExtensions) {
+    if (FeatureFlags.devToolsExtensions.isEnabled) {
       addAutoDisposeListener(
         extensionService.currentExtensions,
         clearRoutesAndSetState,

packages/devtools_app/lib/src/framework/framework_core.dart

@@ -84,7 +84,7 @@ extension FrameworkCore on Never {
     // preferences have been initialized.
     await extensionService.initialize();
 
-    if (FeatureFlags.memoryObserver) {
+    if (FeatureFlags.memoryObserver.isEnabled) {
       _memoryObserver.init();
     }
   }
@@ -99,7 +99,7 @@ extension FrameworkCore on Never {
     preferences.dispose();
     _themeManager?.dispose();
     unawaited(dtdManager.dispose());
-    if (FeatureFlags.memoryObserver) {
+    if (FeatureFlags.memoryObserver.isEnabled) {
       _memoryObserver.dispose();
     }
   }

packages/devtools_app/lib/src/framework/scaffold/scaffold.dart

@@ -58,7 +58,7 @@ class DevToolsScaffold extends StatefulWidget {
 
   static List<Widget> defaultActions({Color? color}) => [
     OpenSettingsAction(color: color),
-    if (FeatureFlags.devToolsExtensions &&
+    if (FeatureFlags.devToolsExtensions.isEnabled &&
         !DevToolsQueryParams.load().hideExtensions)
       ExtensionSettingsAction(color: color),
     ReportFeedbackButton(color: color),

packages/devtools_app/lib/src/framework/scaffold/settings_dialog.dart

@@ -77,7 +77,7 @@ class SettingsDialog extends StatelessWidget {
               gaItem: gac.vmDeveloperMode,
             ),
           ),
-          if (FeatureFlags.wasmOptInSetting) ...[
+          if (FeatureFlags.wasmOptInSetting.isEnabled) ...[
             const SizedBox(height: largeSpacing),
             ...dialogSubHeader(theme, 'Experimental features'),
             Flexible(

packages/devtools_app/lib/src/screens/app_size/app_size_controller.dart

@@ -772,7 +772,7 @@ class AppSizeController extends DevToolsScreenController {
 
   @override
   void releaseMemory({bool partial = false}) {
-    if (FeatureFlags.memoryObserver) {
+    if (FeatureFlags.memoryObserver.isEnabled) {
       // This behavior is the same regardless of the value of `partial`. We can
       // implement a partial clearing if it becomes necessary.
       clear(AppSizeScreen.analysisTabKey);

packages/devtools_app/lib/src/screens/debugger/debugger_controller.dart

@@ -575,7 +575,7 @@ class DebuggerController extends DevToolsScreenController
       );
     }
     // Update the variables for the stack frame:
-    if (FeatureFlags.dapDebugging) {
+    if (FeatureFlags.dapDebugging.isEnabled) {
       serviceConnection.appState.setDapVariables(
         frame != null ? await _createDapVariablesForFrame(frame.frame) : [],
       );

packages/devtools_app/lib/src/screens/debugger/variables.dart

@@ -24,7 +24,7 @@ class Variables extends StatelessWidget {
   Widget build(BuildContext context) {
     // TODO(kenz): preserve expanded state of tree on switching frames and
     // on stepping.
-    if (FeatureFlags.dapDebugging) {
+    if (FeatureFlags.dapDebugging.isEnabled) {
       return TreeView<DapObjectNode>(
         dataRootsListenable: serviceConnection.appState.dapVariables,
         dataDisplayProvider: (variable, onPressed) {

packages/devtools_app/lib/src/screens/inspector_shared/inspector_controls.dart

@@ -30,7 +30,8 @@ class InspectorControls extends StatelessWidget {
     final activeButtonColor = Theme.of(
       context,
     ).colorScheme.activeToggleButtonColor;
-    final isInspectorV2 = controller != null && FeatureFlags.inspectorV2;
+    final isInspectorV2 =
+        controller != null && FeatureFlags.inspectorV2.isEnabled;
     return Row(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [

packages/devtools_app/lib/src/screens/inspector_shared/inspector_screen.dart

@@ -46,7 +46,7 @@ class _InspectorScreenSwitcherState extends State<InspectorScreenSwitcher>
   late InspectorScreenController controller;
 
   bool get shouldShowInspectorV2 =>
-      FeatureFlags.inspectorV2 &&
+      FeatureFlags.inspectorV2.isEnabled &&
       !preferences.inspector.legacyInspectorEnabled.value;
 
   @override

packages/devtools_app/lib/src/screens/inspector_shared/inspector_settings_dialog.dart

@@ -65,7 +65,7 @@ class FlutterInspectorSettingsDialog extends StatelessWidget {
                 const SizedBox(height: largeSpacing),
                 // TODO(https://github.com/flutter/devtools/issues/7860): Clean-up
                 // after Inspector V2 has been released.
-                if (FeatureFlags.inspectorV2)
+                if (FeatureFlags.inspectorV2.isEnabled)
                   Flexible(
                     child: CheckboxSetting(
                       notifier: