Adding a flag to devtools_tools serve for dtd uri (#7191)

tool/lib/commands/serve.dart

diff --git a/tool/lib/commands/serve.dart b/tool/lib/commands/serve.dart
index 365086f..e9d7a25 100644
--- a/tool/lib/commands/serve.dart
+++ b/tool/lib/commands/serve.dart
@@ -13,10 +13,14 @@
 import 'shared.dart';
 
 const _buildAppFlag = 'build-app';
-const _machineFlag = 'machine';
-const _allowEmbeddingFlag = 'allow-embedding';
 const _debugServerFlag = 'debug-server';
 
+// TODO(https://github.com/flutter/devtools/issues/7232): Consider using
+// AllowAnythingParser instead of manually passing these args through.
+const _machineFlag = 'machine';
+const _dtdUriFlag = 'dtd-uri';
+const _allowEmbeddingFlag = 'allow-embedding';
+
 /// This command builds DevTools in release mode by running the
 /// `devtools_tool build` command and then serves DevTools with a locally
 /// running DevTools server.
@@ -80,6 +84,10 @@
         negatable: false,
         help: 'Sets output format to JSON for consumption in tools.',
       )
+      ..addOption(
+        _dtdUriFlag,
+        help: 'Sets the dtd uri when starting the devtools server',
+      )
       ..addFlag(
         _allowEmbeddingFlag,
         help: 'Allow embedding DevTools inside an iframe.',
@@ -114,6 +122,7 @@
     final devToolsAppBuildMode =
         argResults![BuildCommandArgs.buildMode.flagName];
 
+    // Any flag that we aren't removing here is intended to be passed through.
     final remainingArguments = List.of(argResults!.arguments)
       ..remove(BuildCommandArgs.updateFlutter.asArg())
       ..remove(BuildCommandArgs.updateFlutter.asArg(negated: true))