dart2dart: Fix fallthrough in while statements.

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

Index: sdk/lib/_internal/compiler/implementation/dart_backend/dart_codegen.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dart_backend/dart_codegen.dart b/sdk/lib/_internal/compiler/implementation/dart_backend/dart_codegen.dart
index c50c8d5d4aba326757cae2128a6880ed295256b8..2026ca8a956367298ef8ac6763569688831b3fc3 100644
--- a/sdk/lib/_internal/compiler/implementation/dart_backend/dart_codegen.dart
+++ b/sdk/lib/_internal/compiler/implementation/dart_backend/dart_codegen.dart
@@ -190,12 +190,15 @@ class ASTEmitter extends tree.Visitor<dynamic, Expression> {
     Expression condition = new Literal(new dart2js.BoolConstant(true));
     List<Statement> savedBuffer = statementBuffer;
     statementBuffer = <Statement>[];
+    tree.Statement savedFallthrough = fallthrough;
+    fallthrough = stmt.body;
     visitStatement(stmt.body);
     savedBuffer.add(
         new LabeledStatement(
             stmt.label.name,
             new While(condition, new Block(statementBuffer))));
     statementBuffer = savedBuffer;
+    fallthrough = savedFallthrough;
   }
 
   Expression visitConstant(tree.Constant exp) {