Refactor ConstantExpression/ConstantConstructor to use entities.

pkg/compiler/lib/src/constants/constant_constructors.dart

 // Copyright (c) 2015, 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.
 
 // TODO(johnniwinther): Remove this library when all constant constructors are
 // computed during resolution.
 library dart2js.constants.constant_constructors;
 
 import '../common.dart';
 import '../elements/resolution_types.dart';
@@ skipping 269 matching lines @@
   }
 
   @override
   ConstantExpression visitUnary(
       Send node, UnaryOperator operator, Node expression, _) {
     return new UnaryConstantExpression(operator, apply(expression));
   }
 
   @override
   ConstantExpression visitStaticFieldGet(Send node, FieldElement field, _) {
-    return new VariableConstantExpression(field);
+    return new FieldConstantExpression(field);
   }
 
   @override
   ConstantExpression visitTopLevelFunctionGet(
       Send node, MethodElement method, _) {
-    return new FunctionConstantExpression(method);
+    return new FunctionConstantExpression(method, method.type);
   }
 
   @override
   ConstantExpression visitTopLevelFieldGet(Send node, FieldElement field, _) {
-    return new VariableConstantExpression(field);
+    return new FieldConstantExpression(field);
   }
 
   @override
   ConstantExpression visitLiteralInt(LiteralInt node) {
     return new IntConstantExpression(node.value);
   }
 
   @override
   ConstantExpression visitLiteralDouble(LiteralDouble node) {
     return new DoubleConstantExpression(node.value);
@@ skipping 44 matching lines @@
   ConstantExpression visitNamedArgument(NamedArgument node) {
     return apply(node.expression);
   }
 
   @override
   ConstantExpression visitIfNull(Send node, Node left, Node right, _) {
     return new BinaryConstantExpression(
         apply(left), BinaryOperator.IF_NULL, apply(right));
   }
 }