Merge more Kernel infrastructure from kernel_sdk SDK fork.

runtime/lib/mirrors_impl.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.
 
 // VM-specific implementation of the dart:mirrors library.
 
-import "dart:collection" show UnmodifiableListView, UnmodifiableMapView;
-import "dart:async" show Future;
-
 var dirty = false;
 final emptyList = new UnmodifiableListView([]);
 final emptyMap = new UnmodifiableMapView({});
 
 class _InternalMirrorError {
   final String _msg;
   const _InternalMirrorError(String this._msg);
   String toString() => _msg;
 }
 
@@ skipping 1650 matching lines @@
     if (typeMirror == null) {
       typeMirror = makeLocalTypeMirror(key);
       _instantiationCache[key] = typeMirror;
       if (typeMirror is ClassMirror && !typeMirror._isGeneric) {
         _declarationCache[key] = typeMirror;
       }
     }
     return typeMirror;
   }
 }