Fix 56 hints in pkg/compiler

pkg/compiler/lib/src/elements/modelx.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 elements.modelx;
 
 import 'elements.dart';
 import '../constants/expressions.dart';
 import '../constants/constructors.dart';
 import '../helpers/helpers.dart';  // Included for debug helpers.
@@ skipping 807 matching lines @@
               listener.spanFromSpannable(import),
               MessageKind.IMPORTED_HERE,
               {'name': name}),
           enclosingElement, hidingElement);
       importScope[name] = element;
       importers.registerImport(element, import);
     }
 
     if (existing != element) {
       Import existingImport = importers.getImport(existing);
-      Element newElement;
       if (existing.library.isPlatformLibrary &&
           !element.library.isPlatformLibrary) {
         // [existing] is implicitly hidden.
         registerWarnOnUseElement(
             import, MessageKind.HIDDEN_IMPORT, element, existing);
       } else if (!existing.library.isPlatformLibrary &&
                  element.library.isPlatformLibrary) {
         // [element] is implicitly hidden.
         if (import == null) {
           // [element] is imported implicitly (probably through dart:core).
@@ skipping 2378 matching lines @@
   AstElement get definingElement;
 
   bool get hasResolvedAst => definingElement.hasTreeElements;
 
   ResolvedAst get resolvedAst {
     return new ResolvedAst(declaration,
         definingElement.node, definingElement.treeElements);
   }
 
 }