Handle missing break in last switch case

pkg/compiler/lib/src/ssa/builder_kernel.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.
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../closure.dart';
 import '../common.dart';
 import '../common/codegen.dart' show CodegenRegistry;
 import '../common/names.dart';
@@ skipping 1851 matching lines @@
 
       if (isDefaultCase(switchCase)) {
         // An HSwitch has n inputs and n+1 successors, the last being the
         // default case.
         expressionEnd.addSuccessor(block);
         hasDefault = true;
       }
       open(block);
       localsHandler = new LocalsHandler.from(savedLocals);
       buildSwitchCase(switchCase);
+      if (!isAborted() &&
+          switchCase == switchCases.last &&
+          !isDefaultCase(switchCase)) {
+        // If there is no default, we will add one later to avoid
+        // the critical edge. So we generate a break statement to make
+        // sure the last case does not fall through to the default case.
+        jumpHandler.generateBreak();
+      }
       statements.add(
           new HSubGraphBlockInformation(new SubGraph(block, lastOpenedBlock)));
     }
 
     // Add a join-block if necessary.
     // We create [joinBlock] early, and then go through the cases that might
     // want to jump to it. In each case, if we add [joinBlock] as a successor
     // of another block, we also add an element to [caseHandlers] that is used
     // to create the phis in [joinBlock].
     // If we never jump to the join block, [caseHandlers] will stay empty, and
@@ skipping 1798 matching lines @@
     enterBlock.setBlockFlow(
         new HTryBlockInformation(
             kernelBuilder.wrapStatementGraph(bodyGraph),
             exception,
             kernelBuilder.wrapStatementGraph(catchGraph),
             kernelBuilder.wrapStatementGraph(finallyGraph)),
         exitBlock);
     kernelBuilder.inTryStatement = previouslyInTryStatement;
   }
 }