Make continue work in do-while.

frog/leg/resolver.dart

Index: frog/leg/resolver.dart
diff --git a/frog/leg/resolver.dart b/frog/leg/resolver.dart
index 0a1b02284458d0a88696c9c67d4ff4c73fe4d884..801678c00758205bc5e5a379cc9eccf7fab3bf25 100644
--- a/frog/leg/resolver.dart
+++ b/frog/leg/resolver.dart
@@ -1051,6 +1051,7 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
         error(node, MessageKind.NO_CONTINUE_TARGET);
         return;
       }
+      target.isContinueTarget = true;
     } else {
       String labelName = node.target.source.slowToString();
       LabelElement label = statementScope.lookupLabel(labelName);
@@ -1062,8 +1063,8 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
       if (!target.statement.isValidContinueTarget()) {
         error(node.target, MessageKind.INVALID_CONTINUE, [labelName]);
       }
+      label.setContinueTarget();
     }
-    target.isContinueTarget = true;
     mapping[node] = target;
   }