Use the polling watcher by default in pub tests for now.

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

Index: sdk/lib/_internal/pub/test/serve/native_watch_modified_file_test.dart
diff --git a/sdk/lib/_internal/pub/test/serve/watch_modified_file_test.dart b/sdk/lib/_internal/pub/test/serve/native_watch_modified_file_test.dart
similarity index 73%
copy from sdk/lib/_internal/pub/test/serve/watch_modified_file_test.dart
copy to sdk/lib/_internal/pub/test/serve/native_watch_modified_file_test.dart
index 6cf610d3931dc93a811223b259603ed5ed0abe25..883af6dfafebfb6dddce702f0449be3536c3c724 100644
--- a/sdk/lib/_internal/pub/test/serve/watch_modified_file_test.dart
+++ b/sdk/lib/_internal/pub/test/serve/native_watch_modified_file_test.dart
@@ -8,9 +8,13 @@ import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import 'utils.dart';
 
+// TODO(nweiz): Default to testing the native watcher and add an explicit test
+// for the polling watcher when issue 14941 is fixed.
+
 main() {
   initConfig();
-  integration("watches modifications to files", () {
+  integration("watches modifications to files when using the native watcher",
+      () {
     d.dir(appPath, [
       d.appPubspec(),
       d.dir("web", [
@@ -18,7 +22,7 @@ main() {
       ])
     ]).create();
 
-    startPubServe();
+    pubServe(args: ["--no-force-poll"]);
     requestShouldSucceed("index.html", "before");
 
     d.dir(appPath, [