Handle null literal in compile_from_dill

pkg/compiler/lib/src/kernel/element_map.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.
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../common.dart';
 import '../common/names.dart';
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
@@ skipping 15 matching lines @@
 abstract class KernelToElementMap {
   /// Access to the commonly used elements and types.
   CommonElements get commonElements;
 
   /// [ElementEnvironment] for library, class and member lookup.
   ElementEnvironment get elementEnvironment;
 
   /// Returns the [DartType] corresponding to [type].
   DartType getDartType(ir.DartType type);
 
+  /// Returns the [FunctionType] of the [node].
+  FunctionType getFunctionType(ir.FunctionNode node);
+
   /// Returns the list of [DartType]s corresponding to [types].
   List<DartType> getDartTypes(List<ir.DartType> types);
 
   /// Returns the [InterfaceType] corresponding to [type].
   InterfaceType getInterfaceType(ir.InterfaceType type);
 
   /// Return the [InterfaceType] corresponding to the [cls] with the given
   /// [typeArguments].
   InterfaceType createInterfaceType(
       ir.Class cls, List<ir.DartType> typeArguments);
@@ skipping 112 matching lines @@
 enum ForeignKind {
   JS,
   JS_BUILTIN,
   JS_EMBEDDED_GLOBAL,
   JS_INTERCEPTOR_CONSTANT,
   NONE,
 }
 
 abstract class KernelToElementMapMixin implements KernelToElementMap {
   DiagnosticReporter get reporter;
-  FunctionType getFunctionType(ir.FunctionNode node);
   native.BehaviorBuilder get nativeBehaviorBuilder;
   ConstantValue computeConstantValue(ConstantExpression constant);
 
   @override
   Name getName(ir.Name name) {
     return new Name(
         name.name, name.isPrivate ? getLibrary(name.library) : null);
   }
 
   @override
@@ skipping 746 matching lines @@
   TypeMask getInferredTypeOf(MemberEntity member);
 
   /// Returns the inferred type of a dynamic [selector] access on a receiver of
   /// type [mask].
   TypeMask selectorTypeOf(Selector selector, TypeMask mask);
 
   /// Returns the returned type annotation in the [nativeBehavior].
   TypeMask typeFromNativeBehavior(
       native.NativeBehavior nativeBehavior, ClosedWorld closedWorld);
 }