Minor cleanup in inferrer folder

pkg/compiler/lib/src/inferrer/map_tracer.dart

 // Copyright (c) 2014, 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 type_graph_inferrer;
+library compiler.src.inferrer.map_tracer;
+
+import '../elements/elements.dart';
+import '../universe/selector.dart' show Selector;
+
+import 'node_tracer.dart';
+import 'type_graph_nodes.dart';
 
 Set<String> okMapSelectorsSet = new Set.from(
     const <String>[
       // From Object.
       "==",
       "hashCode",
       "toString",
       "noSuchMethod",
       "runtimeType",
       // From Map
@@ skipping 98 matching lines @@
           return;
         }
       }
     } else if (selector.isCall &&
                !info.targets.every((element) => element.isFunction)) {
       bailout('Passed to a closure');
       return;
     }
   }
 }