Add ConstantConstructor to ConstantExpression system.

pkg/compiler/lib/src/compiler.dart

 // Copyright (c) 2012, 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.
 
 part of dart2js;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 834 matching lines @@
   FunctionElement mirrorsUsedConstructor;
 
   // Initialized when dart:mirrors is loaded.
   ClassElement deferredLibraryClass;
 
   /// Document class from dart:mirrors.
   ClassElement documentClass;
   Element identicalFunction;
   Element loadLibraryFunction;
   Element functionApplyMethod;
-  Element intEnvironment;
-  Element boolEnvironment;
-  Element stringEnvironment;
+
+  /// The [int.fromEnvironment] constructor.
+  ConstructorElement intEnvironment;
+
+  /// The [bool.fromEnvironment] constructor.
+  ConstructorElement boolEnvironment;
+
+  /// The [String.fromEnvironment] constructor.
+  ConstructorElement stringEnvironment;
 
   /// Tracks elements with compile-time errors.
   final Set<Element> elementsWithCompileTimeErrors = new Set<Element>();
 
   fromEnvironment(String name) => null;
 
   Element get currentElement => _currentElement;
 
   String tryToString(object) {
     try {
@@ skipping 1565 matching lines @@
     return futureClass.computeType(compiler).createInstantiation([elementType]);
   }
 
   @override
   InterfaceType streamType([DartType elementType = const DynamicType()]) {
     return streamClass.computeType(compiler).createInstantiation([elementType]);
   }
 }
 
 typedef void InternalErrorFunction(Spannable location, String message);