Support field initializers and static/top-level fields in compile_with_dill_test

pkg/compiler/lib/src/kernel/element_map.dart

Index: pkg/compiler/lib/src/kernel/element_map.dart
diff --git a/pkg/compiler/lib/src/kernel/element_map.dart b/pkg/compiler/lib/src/kernel/element_map.dart
index 11e45fcd35566d5d8377d815d8b7b4bef4e8cd45..84904aeae9b21a98313bc63e61e8ec5d9a1f1373 100644
--- a/pkg/compiler/lib/src/kernel/element_map.dart
+++ b/pkg/compiler/lib/src/kernel/element_map.dart
@@ -154,6 +154,10 @@ abstract class KernelToElementMap {
   ConstantValue getConstantValue(ir.Expression expression,
       {bool requireConstant: true, bool implicitNull: false});
 
+  /// Return the [ConstantValue] the initial value of [field] or `null` if
+  /// the initializer is not a constant expression.
+  ConstantValue getFieldConstantValue(ir.Field field);
+
   /// Returns the `noSuchMethod` [FunctionEntity] call from a
   /// `super.noSuchMethod` invocation within [cls].
   FunctionEntity getSuperNoSuchMethod(ClassEntity cls);