Fix hints reported by analyzer.

pkg/compiler/lib/src/ssa/builder.dart

 // Copyright (c) 2012, 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.
 
 import 'dart:collection';
 
 import 'package:js_runtime/shared/embedded_names.dart';
 
 import '../closure.dart';
 import '../common.dart';
@@ skipping 1169 matching lines @@
    * Invariant: [classElement] must be an implementation element.
    */
   void buildFieldInitializers(
       ClassElement classElement, Map<Element, HInstruction> fieldValues) {
     assert(invariant(classElement, classElement.isImplementation));
     classElement.forEachInstanceField(
         (ClassElement enclosingClass, FieldElement member) {
       if (compiler.elementHasCompileTimeError(member)) return;
       reporter.withCurrentElement(member, () {
         ResolvedAst fieldResolvedAst = member.resolvedAst;
-        ast.Node node = fieldResolvedAst.node;
         ast.Expression initializer = fieldResolvedAst.body;
         if (initializer == null) {
           // Unassigned fields of native classes are not initialized to
           // prevent overwriting pre-initialized native properties.
           if (!backend.isNativeOrExtendsNative(classElement)) {
             fieldValues[member] = graph.addConstantNull(closedWorld);
           }
         } else {
           ast.Node right = initializer;
           ResolvedAst savedResolvedAst = resolvedAst;
@@ skipping 5571 matching lines @@
       this.oldReturnLocal,
       this.oldReturnType,
       this.oldResolvedAst,
       this.oldStack,
       this.oldLocalsHandler,
       this.inTryStatement,
       this.allFunctionsCalledOnce,
       this.oldElementInferenceResults)
       : super(function);
 }