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

mojo/dart/embedder/test/dart_to_cpp_tests.cc

Index: mojo/dart/embedder/test/dart_to_cpp_tests.cc
diff --git a/mojo/dart/embedder/test/dart_to_cpp_tests.cc b/mojo/dart/embedder/test/dart_to_cpp_tests.cc
index a772e1f3b9493790364b3e0c5edee682e2a94d97..413f618abda43858ef11ee7183bd49ada871ff7b 100644
--- a/mojo/dart/embedder/test/dart_to_cpp_tests.cc
+++ b/mojo/dart/embedder/test/dart_to_cpp_tests.cc
@@ -303,7 +303,8 @@ class DartToCppTest : public testing::Test {
     // Setup the package root.
     base::FilePath package_root;
     PathService::Get(base::DIR_EXE, &package_root);
-    package_root = package_root.AppendASCII("gen");
+    package_root = package_root.AppendASCII("gen")
+                               .AppendASCII("dart-gen");
 
     config->strict_compilation = true;
     config->script = source;