Include file path in JSON error when possible.

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

Index: sdk/lib/_internal/pub/test/serve/utils.dart
diff --git a/sdk/lib/_internal/pub/test/serve/utils.dart b/sdk/lib/_internal/pub/test/serve/utils.dart
index 0e5d021483fd6b67cc5e7d81f399f8c67eacf53a..d83530f13ea32ce2bdd405f1487083f4bfe8e27f 100644
--- a/sdk/lib/_internal/pub/test/serve/utils.dart
+++ b/sdk/lib/_internal/pub/test/serve/utils.dart
@@ -344,7 +344,7 @@ Future _ensureWebSocket() {
 /// Schedules closing the web socket connection to the currently-running pub
 /// serve.
 Future closeWebSocket() {
-  schedule(() {
+  return schedule(() {

[nweiz, 2014/07/16 18:01:42]

Since this return value is clearly never used, I'd favor making the function
void over returning the future.

[Bob Nystrom, 2014/07/16 18:34:45]

Done.

     return _ensureWebSocket().then((_) => _webSocket.close())
         .then((_) => _webSocket = null);
   }, "closing web socket");