Implement nested switches and missing switch continue targets.

pkg/front_end/lib/src/fasta/kernel/verifier.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library fasta.verifier;
 
 import 'package:kernel/ast.dart'
     show
         InvalidExpression,
         InvalidStatement,
         InvalidInitializer,
         Class,
         ExpressionStatement,
         Field,
         Library,
         Procedure,
         Program,
         TreeNode;
 
 import 'package:kernel/verifier.dart' show VerificationError, VerifyingVisitor;
 
 import '../errors.dart' show printUnexpected;
 
 import 'redirecting_factory_body.dart' show RedirectingFactoryBody;
 
-void verifyProgram(Program program, {bool isOutline: false}) {
+List<VerificationError> verifyProgram(Program program,
+    {bool isOutline: false}) {
   FastaVerifyingVisitor verifier = new FastaVerifyingVisitor(isOutline);
   program.accept(verifier);
-  if (verifier.errors.isNotEmpty) {
-    throw verifier.errors.first;
-  }
+  return verifier.errors;
 }
 
 class FastaVerifyingVisitor extends VerifyingVisitor {
   final List<VerificationError> errors = <VerificationError>[];
 
   String fileUri;
 
   FastaVerifyingVisitor(bool isOutline) {
     this.isOutline = isOutline;
   }
@@ skipping 46 matching lines @@
   @override
   visitInvalidStatement(InvalidStatement node) {
     problem(node, "Invalid statement.");
   }
 
   @override
   visitInvalidInitializer(InvalidInitializer node) {
     problem(node, "Invalid initializer.");
   }
 }