Revert "Merge more Kernel infrastructure from kernel_sdk SDK fork."

runtime/lib/core_patch.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.
 
-import "dart:async";
-import "dart:collection" show LinkedList, LinkedListEntry;
-import 'dart:convert' show ASCII, JSON;
-import "dart:isolate";
 import "dart:math";
 import "dart:typed_data";
-import 'dart:_internal' as internal;
 
 // Equivalent of calling FATAL from C++ code.
 _fatal(msg) native "DartCore_fatal";
 
 // The members of this class are cloned and added to each class that
 // represents an enum type.
 class _EnumHelper {
   String _name;
   String toString() => _name;
   int get hashCode => _name.hashCode;
@@ skipping 54 matching lines @@
         continue;
       }
       return true;
     }
   }
 }
 
 @patch class StackTrace {
   @patch static StackTrace get current native "StackTrace_current";
 }