pkg/compiler: fix imports

pkg/compiler/lib/src/cps_ir/path_based_optimizer.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.path_based_optimizer;
 
+import '../js_backend/js_backend.dart';
+import 'cps_fragment.dart';
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart';
-import 'cps_fragment.dart';
-import '../js_backend/js_backend.dart';
 import 'type_mask_system.dart';
 
 /// Optimizations based on intraprocedural forward dataflow analysis, taking
 /// into account path information that is not expressed by [Refinement] nodes.
 ///
 /// ---
 ///
 /// Removes branches that branch on the same value as a previously seen branch.
 /// For example:
 ///
@@ skipping 146 matching lines @@
 
       // Replace the extra receiver argument with a dummy value if the
       // target definitely does not use it.
       if (typeSystem.targetIgnoresReceiverArgument(
           node.receiver.type, node.selector)) {
         node.makeDummyIntercepted();
       }
     }
   }
 }