Implement do-while in Kernel SSA.

tests/compiler/dart2js/kernel/loops_test.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:test/test.dart';
 
 import 'helper.dart' show check;
 
 main() {
   test('for loop', () {
@@ skipping 13 matching lines @@
 main() {
   var a = 0;
   while (a < 100) {
     a *= 2;
   }
   return a;
 }''';
     return check(code);
   });
 
+  test('do-while loop', () {
+    String code = '''
+main() {
+  var a = 0;
+  do {
+    a *= 2;
+  } while (a < 100);
+  return a;
+}''';
+    return check(code);
+  });
+
   test('for-in loop', () {
     String code = '''
 main() {
   var sum = 0;
   for (var a in [1, 2, 3]) {
     sum += a;
   }
   return sum;
 }''';
     // TODO(het): Check that the code is alpha-equivalent. That is,
@@ skipping 22 matching lines @@
 main() {
   var sum = 0;
   for (a in [1, 2, 3]) {
     sum += a;
   }
   return sum;
 }''';
     return check(code, disableTypeInference: false);
   });
 }