Handle missing break in last switch case

pkg/compiler/lib/src/js_model/locals.dart

 // Copyright (c) 2017, 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 dart2js.js_model.locals;
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../closure.dart';
 import '../common.dart';
@@ skipping 242 matching lines @@
       target = _getJumpTarget(parent);
       target.isContinueTarget = true;
       breaksAsContinue.add(node);
     } else {
       target = _getJumpTarget(node.target);
       target.isBreakTarget = true;
     }
     jumpTargetMap[node] = target;
     super.visitBreakStatement(node);
   }
+
+  @override
+  visitSwitchStatement(ir.SwitchStatement node) {
+    node.expression.accept(this);
+    if (node.cases.isNotEmpty && !node.cases.last.isDefault) {
+      // Ensure that [node] has a corresponding target. We generate a break in
+      // case of a missing break on the last case if it isn't a default case.
+      _getJumpTarget(node);
+    }
+    super.visitSwitchStatement(node);
+  }
 }
 
 class JJumpTarget extends JumpTarget<ir.Node> {
   final MemberEntity memberContext;
   final int nestingLevel;
   List<LabelDefinition<ir.Node>> _labels;
 
   JJumpTarget(this.memberContext, this.nestingLevel);
 
   bool isBreakTarget = false;
@@ skipping 92 matching lines @@
       sb.write(memberContext.enclosingClass.name);
       sb.write('.');
     }
     sb.write(memberContext.name);
     sb.write('#');
     sb.write(name);
     sb.write(')');
     return sb.toString();
   }
 }