Revert "Improvements to causal async stack traces"

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..ed873f38e9b55ac043e5473ee82d3d14a4005221 100644
--- a/runtime/observatory/lib/src/service/object.dart
+++ b/runtime/observatory/lib/src/service/object.dart
@@ -4433,9 +4433,9 @@ class Frame extends ServiceObject implements M.Frame {
       return M.FrameKind.regular;
     }
     switch (frameKind) {
-      case 'Regular': return M.FrameKind.regular;
-      case 'AsyncCausal': return M.FrameKind.asyncCausal;
-      case 'AsyncSuspensionMarker': return M.FrameKind.asyncSuspensionMarker;
+      case 'kRegular': return M.FrameKind.regular;
+      case 'kAsyncCausal': return M.FrameKind.asyncCausal;
+      case 'kAsyncSuspensionMarker': return M.FrameKind.asyncSuspensionMarker;
       default:
         throw new UnsupportedError('Unknown FrameKind: $frameKind');
     }