dart2js cps: Fix some analyzer hints in the CPS backend.

pkg/compiler/lib/src/cps_ir/optimize_interceptors.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.cps_ir.optimize_interceptors;
 
 import 'optimizers.dart';
 import 'cps_ir_nodes.dart';
 import 'loop_hierarchy.dart';
 import 'cps_fragment.dart';
 import '../constants/values.dart';
 import '../elements/elements.dart';
 import '../js_backend/backend_helpers.dart' show BackendHelpers;
 import '../js_backend/js_backend.dart' show JavaScriptBackend;
 import '../types/types.dart' show TypeMask;
 import '../io/source_information.dart' show SourceInformation;
-import '../universe/selector.dart';
 
 /// Replaces `getInterceptor` calls with interceptor constants when possible,
 /// or with "almost constant" expressions like "x && CONST" when the input
 /// is either null or has a known interceptor.
 //
 //  TODO(asgerf): Compute intercepted classes in this pass.
 class OptimizeInterceptors extends TrampolineRecursiveVisitor implements Pass {
   String get passName => 'Optimize interceptors';
 
   JavaScriptBackend backend;
@@ skipping 192 matching lines @@
         sharedConstantFor.remove(prim.value);
       });
     }
     return next;
   }
 
   bool shouldShareConstant(Constant constant) {
     return constant.value.isInterceptor;
   }
 }