Ignore existing ".dart.js" files.

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

Index: sdk/lib/_internal/pub/test/serve/does_not_watch_compiled_js_files_test.dart
diff --git a/sdk/lib/_internal/pub/test/serve/watch_added_file_test.dart b/sdk/lib/_internal/pub/test/serve/does_not_watch_compiled_js_files_test.dart
similarity index 69%
copy from sdk/lib/_internal/pub/test/serve/watch_added_file_test.dart
copy to sdk/lib/_internal/pub/test/serve/does_not_watch_compiled_js_files_test.dart
index 7a42aa19f18f81a53b1be55b060b65549a41a53e..74598695d1dc202092521488afbdd2c0f881fea5 100644
--- a/sdk/lib/_internal/pub/test/serve/watch_added_file_test.dart
+++ b/sdk/lib/_internal/pub/test/serve/does_not_watch_compiled_js_files_test.dart
@@ -10,7 +10,7 @@ import 'utils.dart';
 
 main() {
   initConfig();
-  integration("picks up files added after serving started", () {
+  integration("does not watch changes to compiled JS files in the package", () {
     d.dir(appPath, [
       d.appPubspec(),
       d.dir("web", [
@@ -24,12 +24,14 @@ main() {
 
     d.dir(appPath, [
       d.dir("web", [
-        d.file("other.html", "added")
+        d.file('file.dart', 'void main() => print("hello");'),
+        d.file("other.dart.js", "should be ignored"),
       ])
     ]).create();
 
     waitForBuildSuccess();
-    requestShouldSucceed("other.html", "added");
+    requestShouldSucceed("file.dart", 'void main() => print("hello");');
+    requestShould404("other.dart.js");
     endPubServe();
   });
 }