Uses mojom module names as Dart's package: import URI

mojo/dart/embedder/test/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 
 # These go into the generated source directory for embedder tests.
 copy("copy_dart_mojo_sdk") {
   sources = [
@@ skipping 13 matching lines @@
     "//mojo/public/dart/src/message.dart",
     "//mojo/public/dart/src/message_pipe.dart",
     "//mojo/public/dart/src/natives.dart",
     "//mojo/public/dart/src/proxy.dart",
     "//mojo/public/dart/src/struct.dart",
     "//mojo/public/dart/src/stub.dart",
     "//mojo/public/dart/src/timer_queue.dart",
     "//mojo/public/dart/src/types.dart",
   ]
   outputs = [
-    "{{source_gen_dir}}/{{source_file_part}}",
+    "$root_gen_dir/dart-gen/{{source_root_relative_dir}}/{{source_file_part}}",
   ]
 }
 
 source_set("dart_controller_for_test") {
   testonly = true
   sources = [
     "$root_gen_dir/dart_snapshot.cc",
   ]
 
   deps = [
@@ skipping 25 matching lines @@
     "//mojo/environment:chromium",
     "//testing/gtest",
   ]
 }
 
 copy("expect") {
   sources = [
     "//mojo/dart/testing/expect.dart",
   ]
   outputs = [
-    "{{source_gen_dir}}/{{source_file_part}}",
+    "$root_gen_dir/dart-gen/{{source_root_relative_dir}}/{{source_file_part}}",
   ]
 }
 
 copy("validation_test_input_parser") {
   sources = [
     "//mojo/dart/testing/validation_test_input_parser.dart",
   ]
   outputs = [
-    "{{source_gen_dir}}/{{source_file_part}}",
+    "$root_gen_dir/dart-gen/{{source_root_relative_dir}}/{{source_file_part}}",
   ]
 }
 
 copy("async_helper") {
   sources = [
     "//mojo/dart/testing/async_helper.dart",
   ]
   outputs = [
-    "{{source_gen_dir}}/{{source_file_part}}",
+    "$root_gen_dir/dart-gen/{{source_root_relative_dir}}/{{source_file_part}}",
   ]
 }
 
 source_set("dart_to_cpp_unittests") {
   testonly = true
   sources = [
     "dart_to_cpp_tests.cc",
   ]
   deps = [
     ":dart_controller_for_test",
     ":dart_to_cpp_bindings",
     "//base",
     "//crypto",
     "//mojo/dart/embedder:dart_controller_no_snapshot",
     "//mojo/edk/test:test_support",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/system",
     "//mojo/public/interfaces/bindings/tests:test_interfaces",
     "//testing/gtest",
   ]
 }
 
 mojom("dart_to_cpp_bindings") {
   sources = [
     "dart_to_cpp.mojom",
   ]
 }