Fix filtering out .dart files in release mode.

sdk/lib/_internal/pub/test/serve/does_not_serve_dart_in_release_test.dart

Index: sdk/lib/_internal/pub/test/serve/does_not_serve_dart_in_release_test.dart
diff --git a/sdk/lib/_internal/pub/test/serve/does_not_serve_dart_in_release_test.dart b/sdk/lib/_internal/pub/test/serve/does_not_serve_dart_in_release_test.dart
index b77b4fe1e4b4757028ca6b08c5a79eb18cdcfa7e..1c61497267518f8246dc81f4fd2770f669c87fff 100644
--- a/sdk/lib/_internal/pub/test/serve/does_not_serve_dart_in_release_test.dart
+++ b/sdk/lib/_internal/pub/test/serve/does_not_serve_dart_in_release_test.dart
@@ -11,22 +11,41 @@ import 'utils.dart';
 main() {
   initConfig();
   integration("does not serve .dart files in release mode", () {
+
+    d.dir("foo", [
+      d.libPubspec("foo", "0.0.1"),
+      d.dir("lib", [
+        d.file("foo.dart",
+            """
+            library foo;
+            foo() => 'foo';
+            """)
+      ])
+    ]).create();
+
     d.dir(appPath, [
-      d.appPubspec(),
+      d.appPubspec({
+        "foo": {"path": "../foo"}
+      }),
       d.dir("lib", [
         d.file("lib.dart", "lib() => print('hello');"),
       ]),
       d.dir("web", [
-        d.file("file.dart", "main() => print('hello');"),
+        d.file("file.dart",
+            """
+            import 'package:foo/foo.dart';
+            main() => print('hello');
+            """),
         d.dir("sub", [
           d.file("sub.dart", "main() => 'foo';"),
         ])
       ])
     ]).create();
 
-    pubServe(args: ["--mode", "release"]);
+    pubServe(shouldGetFirst: true, args: ["--mode", "release"]);
     requestShould404("file.dart");
     requestShould404("packages/myapp/lib.dart");
+    requestShould404("packages/foo/foo.dart");
     requestShould404("sub/sub.dart");
     endPubServe();
   });