Add helpers library to dart2js.

sdk/lib/_internal/compiler/implementation/compile_time_constants.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;
 
 /**
  * The [ConstantHandler] keeps track of compile-time constants,
  * initializations of global and static fields, and default values of
  * optional parameters.
@@ skipping 781 matching lines @@
     }
     // Else we don't need to do anything. The final handler is only
     // optimistically trying to compile constants. So it is normal that we
     // sometimes see non-compile time constants.
     // Simply return [:null:] which is used to propagate a failing
     // compile-time compilation.
     return null;
   }
 }
 
-class TryCompileTimeConstantEvaluator extends CompileTimeConstantEvaluator {
-  TryCompileTimeConstantEvaluator(ConstantHandler handler,
-                                  TreeElements elements,
-                                  Compiler compiler)
-      : super(handler, elements, compiler, isConst: true);
-
-  error(Node node, MessageKind message) {
-    // Just fail without reporting it anywhere.
-    throw new CompileTimeConstantError(
-        message, const {}, compiler.terseDiagnostics);
-  }
-}
-
-class CompileTimeConstantError {
-  final Message message;
-  CompileTimeConstantError(MessageKind kind, Map arguments, bool terse)
-    : message = new Message(kind, arguments, terse);
-  String toString() => message.toString();
-}
-
 class ConstructorEvaluator extends CompileTimeConstantEvaluator {
   final FunctionElement constructor;
   final Map<Element, Constant> definitions;
   final Map<Element, Constant> fieldValues;
 
   /**
    * Documentation wanted -- johnniwinther
    *
    * Invariant: [constructor] must be an implementation element.
    */
@@ skipping 169 matching lines @@
           if (fieldValue == null) {
             // Use the default value.
             fieldValue = handler.compileConstant(field);
           }
           jsNewArguments.add(fieldValue);
         },
         includeSuperAndInjectedMembers: true);
     return jsNewArguments;
   }
 }