Fix hints reported by analyzer.

pkg/compiler/lib/src/js_emitter/program_builder/collector.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.
 
 part of dart2js.js_emitter.program_builder;
 
 /**
  * Generates the code for all used classes in the program. Static fields (even
  * in classes) are ignored, since they can be treated as non-class elements.
  *
@@ skipping 263 matching lines @@
 
     for (Element element in Elements.sortedByPosition(elements)) {
       List<Element> list = outputStaticLists.putIfAbsent(
           compiler.deferredLoadTask.outputUnitForElement(element),
           () => new List<Element>());
       list.add(element);
     }
   }
 
   void computeNeededStaticNonFinalFields() {
-    JavaScriptConstantCompiler handler = backend.constants;
     addToOutputUnit(Element element) {
       List<VariableElement> list = outputStaticNonFinalFieldLists.putIfAbsent(
           compiler.deferredLoadTask.outputUnitForElement(element),
           () => new List<VariableElement>());
       list.add(element);
     }
 
     Iterable<Element> fields = compiler
         // TODO(johnniwinther): This should be accessed from a codegen closed
         // world.
@@ skipping 29 matching lines @@
   }
 
   void collect() {
     computeNeededDeclarations();
     computeNeededConstants();
     computeNeededStatics();
     computeNeededStaticNonFinalFields();
     computeNeededLibraries();
   }
 }