Reland "Added --dart-flags option to flutter run (#33924)" (#34181) Reland "Added --dart-flags option to flutter run (#33924)" This reverts commit 587687eedf81aa83521cca96b8fb65a4adc8dd90.

diff --git a/packages/flutter_tools/lib/src/android/android_device.dart b/packages/flutter_tools/lib/src/android/android_device.dart
index c9c5c71..727e25b 100644
--- a/packages/flutter_tools/lib/src/android/android_device.dart
+++ b/packages/flutter_tools/lib/src/android/android_device.dart

@@ -491,6 +491,8 @@
         cmd.addAll(<String>['--ez', 'start-paused', 'true']);
       if (debuggingOptions.disableServiceAuthCodes)
         cmd.addAll(<String>['--ez', 'disable-service-auth-codes', 'true']);
+      if (debuggingOptions.dartFlags.isNotEmpty)
+        cmd.addAll(<String>['--es', 'dart-flags', debuggingOptions.dartFlags]);
       if (debuggingOptions.useTestFonts)
         cmd.addAll(<String>['--ez', 'use-test-fonts', 'true']);
       if (debuggingOptions.verboseSystemLogs) {

diff --git a/packages/flutter_tools/lib/src/commands/run.dart b/packages/flutter_tools/lib/src/commands/run.dart
index 1763364..3fb4bf8 100644
--- a/packages/flutter_tools/lib/src/commands/run.dart
+++ b/packages/flutter_tools/lib/src/commands/run.dart

@@ -4,6 +4,8 @@
 
 import 'dart:async';
 
+import 'package:args/command_runner.dart';
+
 import '../base/common.dart';
 import '../base/file_system.dart';
 import '../base/time.dart';
@@ -130,6 +132,16 @@
         defaultsTo: true,
         help: 'If necessary, build the app before running.',
       )
+      ..addOption('dart-flags',
+        hide: !verboseHelp,
+        help: 'Pass a list of comma separated flags to the Dart instance at '
+              'application startup. Flags passed through this option must be '
+              'present on the whitelist defined within the Flutter engine. If '
+              'a non-whitelisted flag is encountered, the process will be '
+              'terminated immediately.\n\n'
+              'This flag is not available on the stable channel and is only '
+              'applied in debug and profile modes. This option should only '
+              'be used for experiments and should not be used by typical users.')
       ..addOption('use-application-binary',
         hide: !verboseHelp,
         help: 'Specify a pre-built application binary to use when running.',
@@ -294,6 +306,7 @@
         buildInfo,
         startPaused: argResults['start-paused'],
         disableServiceAuthCodes: argResults['disable-service-auth-codes'],
+        dartFlags: argResults['dart-flags'] ?? '',
         useTestFonts: argResults['use-test-fonts'],
         enableSoftwareRendering: argResults['enable-software-rendering'],
         skiaDeterministicRendering: argResults['skia-deterministic-rendering'],
@@ -350,6 +363,11 @@
       );
     }
 
+    if (argResults['dart-flags'] != null && FlutterVersion.instance.isStable) {
+      throw UsageException('--dart-flags is not available on the stable '
+                           'channel.', null);
+    }
+
     for (Device device in devices) {
       if (await device.isLocalEmulator) {
         if (await device.supportsHardwareRendering) {

diff --git a/packages/flutter_tools/lib/src/device.dart b/packages/flutter_tools/lib/src/device.dart
index 394befb..3947ce3 100644
--- a/packages/flutter_tools/lib/src/device.dart
+++ b/packages/flutter_tools/lib/src/device.dart

@@ -377,6 +377,7 @@
     this.buildInfo, {
     this.startPaused = false,
     this.disableServiceAuthCodes = false,
+    this.dartFlags = '',
     this.enableSoftwareRendering = false,
     this.skiaDeterministicRendering = false,
     this.traceSkia = false,
@@ -391,6 +392,7 @@
     : debuggingEnabled = false,
       useTestFonts = false,
       startPaused = false,
+      dartFlags = '',
       disableServiceAuthCodes = false,
       enableSoftwareRendering = false,
       skiaDeterministicRendering = false,
@@ -404,6 +406,7 @@
 
   final BuildInfo buildInfo;
   final bool startPaused;
+  final String dartFlags;
   final bool disableServiceAuthCodes;
   final bool enableSoftwareRendering;
   final bool skiaDeterministicRendering;

diff --git a/packages/flutter_tools/lib/src/ios/devices.dart b/packages/flutter_tools/lib/src/ios/devices.dart
index 02ede71..15f2a2e 100644
--- a/packages/flutter_tools/lib/src/ios/devices.dart
+++ b/packages/flutter_tools/lib/src/ios/devices.dart

@@ -283,6 +283,11 @@
     if (debuggingOptions.disableServiceAuthCodes)
       launchArguments.add('--disable-service-auth-codes');
 
+    if (debuggingOptions.dartFlags.isNotEmpty) {
+      final String dartFlags = debuggingOptions.dartFlags;
+      launchArguments.add('--dart-flags="$dartFlags"');
+    }
+
     if (debuggingOptions.useTestFonts)
       launchArguments.add('--use-test-fonts');