Prepare for decoupling analyzer ASTs from element model.

pkg/analyzer/benchmark/errors_in_all_libraries.dart

 #!/usr/bin/env dart
 // Copyright (c) 2016, 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.
 
 /// Resolves this library and everything it transitively imports and generates
 /// errors in all of those libraries. Does this in an infinite loop, starting
 /// from scratch each time, to show how VM warm-up affects things and to make
 /// it easier to connect to this with observatory.
 import 'dart:io';
 
+import 'package:analyzer/dart/ast/resolution_accessors.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
 import 'package:analyzer/src/context/builder.dart';
 import 'package:analyzer/src/dart/sdk/sdk.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/source/source_resource.dart';
@@ skipping 32 matching lines @@
 
     var mainSource =
         new FileSource(resourceProvider.getFile(p.fromUri(Platform.script)));
     context.applyChanges(new ChangeSet()..addedSource(mainSource));
 
     var initialLibrary =
         context.resolveCompilationUnit2(mainSource, mainSource);
 
     // Walk all of the transitively referenced libraries and compute errors.
     var errorCount = 0;
-    var allLibraries = _reachableLibraries(initialLibrary.element.library);
+    var allLibraries =
+        _reachableLibraries(elementForCompilationUnit(initialLibrary).library);
     for (var lib in allLibraries) {
       for (var unit in lib.units) {
         var source = unit.source;
 
         // Skip core libraries.
         if (source.uri.scheme == 'dart') continue;
 
         var librarySource = context.getLibrariesContaining(source).single;
         context.resolveCompilationUnit2(source, librarySource);
         errorCount += context.computeErrors(source).length;
@@ skipping 14 matching lines @@
     if (seen.contains(lib)) return;
     seen.add(lib);
     results.add(lib);
     lib.importedLibraries.forEach(find);
     lib.exportedLibraries.forEach(find);
   }
 
   find(start);
   return results;
 }