Cleanup warnings in unit tests.

tests/compiler/dart2js/memory_compiler.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 dart2js.test.memory_compiler;
 
 import 'memory_source_file_helper.dart';
 
 import 'package:compiler/implementation/dart2jslib.dart'
        show NullSink;
@@ skipping 152 matching lines @@
                                    packageRoot,
                                    options,
                                    {});
   if (cachedCompiler != null) {
     compiler.coreLibrary =
         cachedCompiler.libraryLoader.lookupLibrary(Uri.parse('dart:core'));
     compiler.types = cachedCompiler.types.copy(compiler);
     Map copiedLibraries = {};
     cachedCompiler.libraryLoader.libraries.forEach((library) {
       if (library.isPlatformLibrary) {
-        compiler.libraryLoader.mapLibrary(library);
+        var libraryLoader = compiler.libraryLoader;
+        libraryLoader.mapLibrary(library);
         compiler.onLibraryCreated(library);
         compiler.onLibraryScanned(library, null);
         if (library.isPatched) {
           var patchLibrary = library.patch;
           compiler.onLibraryCreated(patchLibrary);
           compiler.onLibraryScanned(patchLibrary, null);
         }
         copiedLibraries[library.canonicalUri] = library;
       }
     });
@@ skipping 60 matching lines @@
       createDiagnosticHandler(diagnosticHandler, provider, showDiagnostics);
 
   List<Uri> libraries = <Uri>[];
   memorySourceFiles.forEach((String path, _) {
     libraries.add(new Uri(scheme: 'memory', path: path));
   });
 
   return analyze(libraries, libraryRoot, packageRoot,
                  provider, handler, options);
 }