Work around issue 11901 in stack_trace.

pkg/stack_trace/lib/src/frame.dart

Index: pkg/stack_trace/lib/src/frame.dart
diff --git a/pkg/stack_trace/lib/src/frame.dart b/pkg/stack_trace/lib/src/frame.dart
index 3bead03ba0f785e8fafbde2c958412e022f48e9b..6a88a268c93a6d09d8064c81090dd9713ace6b7b 100644
--- a/pkg/stack_trace/lib/src/frame.dart
+++ b/pkg/stack_trace/lib/src/frame.dart
@@ -118,6 +118,10 @@ class Frame {
     // always be found. The column is optional.
     var member = match[1].replaceAll("<anonymous closure>", "<fn>");
     var uri = Uri.parse(match[2]);
+    // Work around issue 11901.
+    if (uri == new Uri(path: 'timer_impl.dart')) {
+      uri = Uri.parse('dart:async/timer_impl.dart');
+    }
     var line = int.parse(match[3]);
     var column = null;
     var columnMatch = match[4];