Add location information to the JSON reporter.

lib/src/runner/engine.dart

Index: lib/src/runner/engine.dart
diff --git a/lib/src/runner/engine.dart b/lib/src/runner/engine.dart
index 54c312d02d0669934cfd342fe0bef6274fa0ffb2..ba17aced58f963cd909af5d84ac16c8aa7da3089 100644
--- a/lib/src/runner/engine.dart
+++ b/lib/src/runner/engine.dart
@@ -365,7 +365,8 @@ class Engine {
   Future _runSkippedTest(LiveSuiteController suiteController, GroupEntry entry,
       List<Group> parents) {
     // The netry name will be `null` for the root group.
-    var test = new LocalTest(entry.name ?? "(suite)", entry.metadata, () {});
+    var test = new LocalTest(entry.name ?? "(suite)", entry.metadata, () {},
+        trace: entry.trace);
 
     var controller;
     controller = new LiveTestController(