Optimize DDC private library files.

pkg/dev_compiler/tool/input_sdk/private/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._js_helper;
 
 /// Tells the optimizing compiler to always inline the annotated method.
 class ForceInline {
   const ForceInline();
 }
 
+/// Marks a variable or API to be non-nullable
+/// Currently unchecked
+/// TODO(leafp): Consider adding static checking and exposing
+/// this to user code.
+class NotNull {
+  const NotNull();
+}
+
+const notNull = const NotNull();
+
+/// Tells the development compiler to check a variable for null at its
+/// declaration point, and then to assume that the variable is non-null
+/// from that point forward.
+class NullCheck {
+  const NullCheck();
+}
+
+const nullCheck = const NullCheck();
+
 /// 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();
 }
@@ skipping 10 matching lines @@
   /// matching the JavaScript calling conventions.
   final String name;
   const JsPeerInterface({this.name});
 }
 
 /// A Dart interface may only be implemented by a native JavaScript object
 /// if it is marked with this annotation.
 class SupportJsExtensionMethods {
   const SupportJsExtensionMethods();
 }