Use common.dart to re-export commonly used entities.

pkg/compiler/lib/src/inferrer/inferrer_visitor.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.
 
 library inferrer_visitor;
 
 import 'dart:collection' show
     IterableMixin;
 
+import '../common.dart';
 import '../compiler.dart' show
     Compiler;
 import '../constants/constant_system.dart';
 import '../constants/expressions.dart';
 import '../dart_types.dart';
-import '../diagnostics/diagnostic_listener.dart' show
-    DiagnosticReporter;
-import '../diagnostics/spannable.dart' show
-    Spannable;
 import '../elements/elements.dart';
 import '../resolution/operators.dart';
 import '../resolution/semantic_visitor.dart';
 import '../resolution/send_resolver.dart' show
     SendResolverMixin;
 import '../resolution/tree_elements.dart' show
     TreeElements;
 import '../tree/tree.dart';
 import '../types/types.dart' show
     TypeMask;
@@ skipping 1509 matching lines @@
     return type;
   }
 
   T visitCascade(Cascade node) {
     // Ignore the result of the cascade send and return the type of the cascade
     // receiver.
     visit(node.expression);
     return cascadeReceiverStack.removeLast();
   }
 }