The file isolte_runtime.dart was only used by the analyzer, and now it is no longer in use

tools/create_sdk.py

 #!/usr/bin/env python
 #
 # 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.
 #
 # A script which will be invoked from gyp to create an SDK.
 #
 # Usage: create_sdk.py sdk_directory
 #
@@ skipping 341 matching lines @@
       ("../../../../corelib/src/", "../../../core/runtime/")
     ]);
   ReplaceInFiles([join(LIB, 'dartdoc', 'frog', 'lib', 'corelib_impl.dart')], [
       ("../../../../corelib/src/implementation", "../../../coreimpl/runtime/")
     ]);
 
   # Create and populate lib/isolate
   copytree(join(HOME, 'lib', 'isolate'), join(LIB, 'isolate'),
            ignore=ignore_patterns('.svn'))
 
-  isolate_runtime_dir = join(LIB, 'isolate', 'runtime')
-  # path seems to exist when run locally, but not on builder
-  if not exists(isolate_runtime_dir):
-    os.makedirs(isolate_runtime_dir)
-
-  isolate_runtime_src = join(HOME, 'runtime', 'lib', 'isolate.dart')
-  isolate_runtime_dest = join(LIB, 'isolate', 'runtime', 'isolate.dart')
-  copyfile(isolate_runtime_src, isolate_runtime_dest)
-
   #
   # Create and populate lib/core.
   #
 
   # First, copy corelib/* to lib/runtime
   for filename in corelib_sources:
     for target_dir in ['runtime']:
       copyfile(join('corelib', 'src', filename),
                join(corelib_dest_dir, target_dir, filename))
 
@@ skipping 90 matching lines @@
   if revision is not None:
     with open(os.path.join(SDK_tmp, 'revision'), 'w') as f:
       f.write(revision + '\n')
       f.close()
 
   move(SDK_tmp, SDK)
   utils.Touch(os.path.join(SDK, 'create.stamp'))
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv))