Implement correct scoping rules for variables.

sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart

Index: sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart b/sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart
index 57ee07ace938c2c531a4275e4dcdbe82fff5c858..720edc69f3eeab69926606c1b71560b06f9ccebd 100644
--- a/sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart
+++ b/sdk/lib/_internal/compiler/implementation/dart_backend/utils.dart
@@ -25,7 +25,9 @@ class CloningVisitor implements Visitor<Node> {
     return clone;
   }
 
-  visitBlock(Block node) => new Block(visit(node.statements));
+  visitBlock(Block node) {
+    return new Block(visit(node.statements), node.declarations);
+  }
 
   visitBreakStatement(BreakStatement node) => new BreakStatement(
       visit(node.target), node.keywordToken, node.semicolonToken);
@@ -187,7 +189,7 @@ class CloningVisitor implements Visitor<Node> {
 
   visitSwitchCase(SwitchCase node) => new SwitchCase(
       visit(node.labelsAndCases), node.defaultKeyword, visit(node.statements),
-      node.startToken);
+      node.startToken, node.declarations);
 
   visitSwitchStatement(SwitchStatement node) => new SwitchStatement(
       visit(node.parenthesizedExpression), visit(node.cases),