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

pkg/compiler/lib/src/resolution/send_resolver.dart

 // Copyright (c) 2015, 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.semantics_visitor.resolver;
 
+import '../common.dart';
 import '../constants/expressions.dart';
 import '../dart_types.dart';
-import '../diagnostics/messages.dart' show
-    MessageKind;
-import '../diagnostics/spannable.dart' show
-    Spannable,
-    SpannableAssertionFailure;
 import '../elements/elements.dart';
 import '../tree/tree.dart';
 import '../universe/call_structure.dart' show
     CallStructure;
 import '../universe/selector.dart' show
     Selector;
 
 import 'access_semantics.dart';
 import 'semantic_visitor.dart';
 import 'send_structure.dart';
@@ skipping 448 matching lines @@
       return internalError(node, "Unexpected variable $element.");
     }
     if (element.isConst) {
       ConstantExpression constant = elements.getConstant(element.initializer);
       return new ConstantVariableStructure(kind, node, element, constant);
     } else {
       return new NonConstantVariableStructure(kind, node, element);
     }
   }
 }