Change the type of google3WorkspaceRoot to Uri | String.

A subsequent CL will be sent to change this to String, after
flutter_tools is migrated to pass a String instead of a Uri.

BazelUriConverter treats google3WorkspaceRoot as a String. Passing a Uri
causes the debug adapter to pass `--google3-workspace-root=file:///`
when launching DDS, making it fail to resolve the uris.

Bug: b/364942683
Change-Id: I46f366bb2308a107a68e63445138e071432e45de
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/383901
Reviewed-by: Ben Konyi <bkonyi@google.com>
Auto-Submit: Chingjun Lau <chingjun@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>
diff --git a/pkg/dds/lib/dds_launcher.dart b/pkg/dds/lib/dds_launcher.dart
index 7a0de08..371476e 100644
--- a/pkg/dds/lib/dds_launcher.dart
+++ b/pkg/dds/lib/dds_launcher.dart
@@ -53,8 +53,12 @@
     bool enableServicePortFallback = false,
     List<String> cachedUserTags = const <String>[],
     String? dartExecutable,
-    Uri? google3WorkspaceRoot,
+    // TODO(chingjun): Change the type to String once flutter_tools is migrated.
+    Object? google3WorkspaceRoot,
   }) async {
+    assert(google3WorkspaceRoot == null ||
+        google3WorkspaceRoot is Uri ||
+        google3WorkspaceRoot is String);
     final process = await Process.start(
       dartExecutable ?? Platform.executable,
       <String>[