pkg/compiler: fix imports

pkg/compiler/lib/src/cps_ir/use_field_initializers.dart

 // Copyright (c) 2016, 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.
 library dart2js.cps_ir.use_field_initializers;
 
+import '../elements/elements.dart';
+import '../js_backend/js_backend.dart';
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart';
-import '../elements/elements.dart';
-import '../js_backend/js_backend.dart';
 
 /// Eliminates [SetField] instructions when the value can instead be passed into
 /// the field initializer of a [CreateInstance] instruction.
 ///
 /// This compensates for a somewhat common pattern where fields are initialized
 /// in the constructor body instead of using initializers. For example:
 ///
 ///     class Foo {
 ///       var x, y;
 ///       Foo(x, y) {
@@ skipping 191 matching lines @@
 }
 
 class EscapeVisitor extends DeepRecursiveVisitor {
   final UseFieldInitializers main;
   EscapeVisitor(this.main);
 
   processReference(Reference ref) {
     main.escape(ref);
   }
 }