sdk files reorganization to make dart2js a proper package

sdk/lib/_internal/compiler/js_lib/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 _js_helper;
-
-/// Tells the optimizing compiler that the annotated method has no
-/// side-effects. Allocations don't count as side-effects, since they can be
-/// dropped without changing the semantics of the program.
-///
-/// Requires @NoInline() to function correctly.
-class NoSideEffects {
-  const NoSideEffects();
-}
-
-/// Tells the optimizing compiler that the annotated method cannot throw.
-/// Requires @NoInline() to function correctly.
-class NoThrows {
-  const NoThrows();
-}
-
-/// Tells the optimizing compiler to not inline the annotated method.
-class NoInline {
-  const NoInline();
-}
-
-/// Tells the optimizing compiler to always inline the annotated method.
-class ForceInline {
-  const ForceInline();
-}
-
-// Ensures that the annotated method is represented internally using
-// IR nodes ([:value == true:]) or AST nodes ([:value == false:]).
-class IrRepresentation {
-  final bool value;
-  const IrRepresentation(this.value);
-}
-
-/// Marks a class as native and defines its JavaScript name(s).
-class Native {
-  final String name;
-  const Native(this.name);
-}
-
-class _Patch {
-  final String version;
-
-  const _Patch(this.version);
-}
-
-/// Annotation that marks the declaration as a patch.
-const _Patch patch = const _Patch(null);
-
-/// Annotation that marks the declaration as a patch for the old emitter.
-const _Patch patch_old = const _Patch('old');
-
-/// Annotation that marks the declaration as a patch for the new emitter.
-const _Patch patch_new = const _Patch('new');