Create 'unified' version of Date, with a dart2js implementation.

lib/compiler/implementation/library_map.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.
 
 // TODO(ahe): Long term, it would probably be better if we do not use
 // executable code to define the locations of libraries.
 
 #library('library_map');
 /**
  * Simple struct holding the path to a library and an optional path
@@ skipping 11 matching lines @@
 }
 
 /**
  * Specifies the location of Dart platform libraries.
  */
 final Map<String, LibraryInfo> DART2JS_LIBRARY_MAP
     = const <LibraryInfo> {
   "core": const LibraryInfo(
       "lib/compiler/implementation/lib/core.dart"),
   "coreimpl": const LibraryInfo(
-      "lib/compiler/implementation/lib/coreimpl.dart"),
+      "lib/compiler/implementation/lib/coreimpl.dart",
+      "lib/compiler/implementation/lib/coreimpl.dartp"),
   "_js_helper": const LibraryInfo(
       "lib/compiler/implementation/lib/js_helper.dart", isInternal: true),
   "_interceptors": const LibraryInfo(
       "lib/compiler/implementation/lib/interceptors.dart", isInternal: true),
   "crypto": const LibraryInfo(
       "lib/crypto/crypto.dart"),
   "dom_deprecated": const LibraryInfo(
       "lib/dom/dart2js/dom_dart2js.dart", isInternal: true),
   "html": const LibraryInfo(
       "lib/html/dart2js/html_dart2js.dart"),
   "io": const LibraryInfo(
       "lib/compiler/implementation/lib/io.dart"),
   "isolate": const LibraryInfo(
       "lib/isolate/isolate_dart2js.dart"),
   "json": const LibraryInfo("lib/json/json.dart"),
   "math": const LibraryInfo(
       "corelib/unified/math/math.dart",
       "lib/compiler/implementation/lib/math.dartp", isInternal: true),
   "uri": const LibraryInfo("lib/uri/uri.dart"),
   "utf": const LibraryInfo("lib/utf/utf.dart"),
   "web": const LibraryInfo("lib/web/web.dart"),
 };