dart2js: Add a header to the output of the startup emitter.

pkg/compiler/lib/src/js_emitter/full_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.full_emitter;
 
 /// Enables debugging of fast/slow objects using V8-specific primitives.
 const DEBUG_FAST_OBJECTS = false;
 
 /**
  * Call-back for adding property with [name] and [value].
  */
 typedef jsAst.Property AddPropertyFunction(jsAst.Name name,
                                            jsAst.Expression value);
 
-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]
-//    method.
-//
-// dartMainRunner(main, args):
-//    if this function is defined, the Dart [main] method will not be invoked
-//    directly. Instead, a closure that will invoke [main], and its arguments
-//    [args] is passed to [dartMainRunner].
-//
-// dartDeferredLibraryLoader(uri, successCallback, errorCallback):
-//    if this function is defined, it will be called when a deferered library
-//    is loaded. It should load and eval the javascript of `uri`, and call
-//    successCallback. If it fails to do so, it should call errorCallback with
-//    an error.
-""";
-
 // Compact field specifications.  The format of the field specification is
 // <accessorName>:<fieldName><suffix> where the suffix and accessor name
 // prefix are optional.  The suffix directs the generation of getter and
 // setter methods.  Each of the getter and setter has two bits to determine
 // the calling convention.  Setter listed below, getter is similar.
 //
 //     00: no setter
 //     01: function(value) { this.field = value; }
 //     10: function(receiver, value) { receiver.field = value; }
 //     11: function(receiver, value) { this.field = value; }
 //
 // The suffix encodes 4 bits using three ASCII ranges of non-identifier
 // 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;