Add helpers library to dart2js.

sdk/lib/_internal/compiler/implementation/js_emitter/declarations.dart

 // Copyright (c) 2013, 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.js_emitter;
 
 /// Enables debugging of fast/slow objects using V8-specific primitives.
 const DEBUG_FAST_OBJECTS = false;
 
 /**
@@ skipping 28 matching lines @@
                          String name,
                          String accessorName,
                          bool needsGetter,
                          bool needsSetter,
                          bool needsCheckedSetter);
 
 // Function signatures used in the generation of runtime type information.
 typedef void FunctionTypeSignatureEmitter(Element method,
                                           FunctionType methodType);
 
-// TODO(johnniwinther): Clean up terminology for rti in the emitter.
-typedef void FunctionTypeTestEmitter(FunctionType functionType);
-
 typedef void SubstitutionEmitter(Element element, {bool emitNull});
 
 const String GENERATED_BY = """
 // Generated by dart2js, the Dart to JavaScript compiler.
 """;
 
 const String HOOKS_API_USAGE = """
 // The code supports the following hooks:
 // dartPrint(message):
 //    if this function is defined it is called instead of the Dart [print]
@@ skipping 20 matching lines @@
 // characters.
 const FIELD_CODE_CHARACTERS = r"<=>?@{|}~%&'()*";
 const NO_FIELD_CODE = 0;
 const FIRST_FIELD_CODE = 1;
 const RANGE1_FIRST = 0x3c;   //  <=>?@    encodes 1..5
 const RANGE1_LAST = 0x40;
 const RANGE2_FIRST = 0x7b;   //  {|}~     encodes 6..9
 const RANGE2_LAST = 0x7e;
 const RANGE3_FIRST = 0x25;   //  %&'()*+  encodes 10..16
 const RANGE3_LAST = 0x2b;