Add --verify-ir flag to dartk and test.py.

pkg/compiler/lib/src/kernel/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.md file.
 
 import 'dart:async';
 import 'dart:collection' show Queue;
 
 import 'package:kernel/ast.dart' as ir;
-import 'package:kernel/checks.dart' show CheckParentPointers;
+import 'package:kernel/verifier.dart' show CheckParentPointers;
 
 import '../common.dart';
 import '../common/names.dart';
 import '../compiler.dart' show Compiler;
 import '../constants/expressions.dart' show TypeConstantExpression;
 import '../dart_types.dart'
     show DartType, FunctionType, InterfaceType, TypeKind, TypeVariableType;
 import '../diagnostics/messages.dart' show MessageKind;
 import '../diagnostics/spannable.dart' show Spannable;
 import '../elements/elements.dart'
@@ skipping 734 matching lines @@
 }
 
 class ConstructorTarget {
   final ConstructorElement element;
   final DartType type;
 
   ConstructorTarget(this.element, this.type);
 
   String toString() => "ConstructorTarget($element, $type)";
 }