Remove dart2js specific core.dart and coreimpl.dart files.

lib/_internal/libraries.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.
 
 #library('libraries');
 
 /**
  * A bit flag used by [LibraryInfo] indicating that a library is used by dart2js
  */
 const int DART2JS_PLATFORM = 1;
 
 /**
  * A bit flag used by [LibraryInfo] indicating that a library is used by the VM
  */
 const int VM_PLATFORM = 2;
 
 /**
  * Mapping of "dart:" library name (e.g. "core") to information about that library.
  * This information is structured such that Dart Editor can parse this file
  * and extract the necessary information without executing it
  * while other tools can access via execution.
  */
 const Map<String, LibraryInfo> LIBRARIES = const <LibraryInfo> {
 
   "core": const LibraryInfo(
       "core/core.dart",
-      dart2jsPath: "compiler/implementation/lib/core.dart",
       dart2jsPatchPath: "compiler/implementation/lib/core_patch.dart"),
 
   "coreimpl": const LibraryInfo(
       "coreimpl/coreimpl.dart",
       implementation: true,
-      dart2jsPath: "compiler/implementation/lib/coreimpl.dart",
       dart2jsPatchPath: "compiler/implementation/lib/coreimpl_patch.dart"),
 
   "crypto": const LibraryInfo(
       "crypto/crypto.dart"),
 
   "html": const LibraryInfo(
       "html/dartium/html_dartium.dart",
       category: "Client",
       dart2jsPath: "html/dart2js/html_dart2js.dart"),
 
@@ skipping 98 matching lines @@
            this.category = "Shared",
            this.dart2jsPath,
            this.dart2jsPatchPath,
            this.implementation = false,
            this.documented = true,
            this.platforms = DART2JS_PLATFORM | VM_PLATFORM]);
 
   bool get isDart2jsLibrary => (platforms & DART2JS_PLATFORM) != 0;
   bool get isVmLibrary => (platforms & VM_PLATFORM) != 0;
 }