Fix causal_async_star_stack_contents_test with optimization-counter-threshold=5

runtime/observatory/lib/src/service/object.dart

Index: runtime/observatory/lib/src/service/object.dart
diff --git a/runtime/observatory/lib/src/service/object.dart b/runtime/observatory/lib/src/service/object.dart
index 7a2780b30ecfe715d29b1a724a32cbb9ca63b55a..32a3548d30cba193d02626cb47b5aba4bf33c666 100644
--- a/runtime/observatory/lib/src/service/object.dart
+++ b/runtime/observatory/lib/src/service/object.dart
@@ -4404,6 +4404,14 @@ class ServiceMetric extends ServiceObject implements M.Metric {
   String toString() => "ServiceMetric($_id)";
 }
 
+void printFrames(List<Frame> frames) async {
+  for (int i = 0; i < frames.length; i++) {
+    final Frame frame = frames[i];
+    String frameText = await frame.toUserString();
+    print('#${i.toString().padLeft(3)}: $frameText');
+  }
+}
+
 class Frame extends ServiceObject implements M.Frame {
   M.FrameKind kind = M.FrameKind.regular;
   int index;
@@ -4450,6 +4458,17 @@ class Frame extends ServiceObject implements M.Frame {
       return "Frame([$kind])";
     }
   }
+
+  String toUserString() async {
+    if (function != null) {
+      return "Frame([$kind] ${function.qualifiedName} "
+             "${await location.toUserString()})";
+    } else if (location != null) {
+      return "Frame([$kind] ${await location.toUserString()}";
+    } else {
+      return "Frame([$kind])";
+    }
+  }
 }
 
 class ServiceMessage extends ServiceObject {