Change how we provide value previews in the vm service.

runtime/bin/vmservice/client/lib/src/elements/instance_ref.dart

Index: runtime/bin/vmservice/client/lib/src/elements/instance_ref.dart
diff --git a/runtime/bin/vmservice/client/lib/src/elements/instance_ref.dart b/runtime/bin/vmservice/client/lib/src/elements/instance_ref.dart
index c97e484dfc70b75ff96a5fa4b1021d0934dd3eb6..4fddfbb5a3c2ca74357e13223b7aded1be8e112a 100644
--- a/runtime/bin/vmservice/client/lib/src/elements/instance_ref.dart
+++ b/runtime/bin/vmservice/client/lib/src/elements/instance_ref.dart
@@ -40,9 +40,9 @@ class InstanceRefElement extends ServiceRefElement {
     assert(ref is ServiceMap);
     if (expand) {
       ref.reload().then((result) {
-        if (result['preview'] != null) {
-          result.name = result['preview'];
-          result.vmName = result['preview'];
+        if (result['valueAsString'] != null) {
+          result.name = result['valueAsString'];
+          result.vmName = result['valueAsString'];
         }
         ref = result;
         notifyPropertyChange(#ref, 0, 1);