[flutter] prepare for migrating fuchsia_remote_debug_protocol to null safety

Change-Id: I06f27cae491b2464d4b99d6e53102d74382b12eb
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/476557
Reviewed-by: Naud Ghebre <naudzghebre@google.com>
Commit-Queue: Chase Latta <chaselatta@google.com>
diff --git a/build/secondary/third_party/dart-pkg/git/flutter/packages/fuchsia_remote_debug_protocol/BUILD.gn b/build/secondary/third_party/dart-pkg/git/flutter/packages/fuchsia_remote_debug_protocol/BUILD.gn
index fa79ebd..7381dbc 100644
--- a/build/secondary/third_party/dart-pkg/git/flutter/packages/fuchsia_remote_debug_protocol/BUILD.gn
+++ b/build/secondary/third_party/dart-pkg/git/flutter/packages/fuchsia_remote_debug_protocol/BUILD.gn
@@ -9,6 +9,8 @@
 
   disable_analysis = true
 
+  pubspec = "//third_party/dart-pkg/git/flutter/packages/fuchsia_remote_debug_protocol/pubspec.yaml"
+
   sources = [
     "fuchsia_remote_debug_protocol.dart",
     "logging.dart",