Revert "Change some platform libraries to use `part of URI`."

sdk/lib/core/annotations.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.
 
-part of "dart:core";
+part of dart.core;
 
 /**
  * The annotation `@Deprecated('expires when')` marks a feature as deprecated.
  *
  * The annotation `@deprecated` is a shorthand for deprecating until
  * an unspecified "next release".
  *
  * The intent of the `@Deprecated` annotation is to inform users of a feature
  * that they should change their code, even if it is currently still working
  * correctly.
@@ skipping 128 matching lines @@
  *
  * A class that marked as `@proxy` should override the `noSuchMethod`
  * declared on [Object].
  *
  * The intent of the `@proxy` notation is to create objects that implement a
  * type (or multiple types) that are not known at compile time. If the types
  * are known at compile time, a class can be written that implements these
  * types.
  */
 const Object proxy = const _Proxy();