Move getElementAt() to CompilationUnitElement.

pkg/analyzer/lib/src/generated/incremental_resolver.dart

 // Copyright (c) 2014, 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 engine.incremental_resolver;
 
 import 'dart:collection';
 import 'dart:math' as math;
 
 import 'package:analyzer/src/generated/constant.dart';
@@ skipping 770 matching lines @@
 }
 
 /**
  * Instances of the class [IncrementalResolver] resolve the smallest portion of
  * an AST structure that we currently know how to resolve.
  */
 class IncrementalResolver {
   /**
    * The element of the compilation unit being resolved.
    */
-  final CompilationUnitElement _definingUnit;
+  final CompilationUnitElementImpl _definingUnit;
 
   /**
    * The context the compilation unit being resolved in.
    */
   AnalysisContextImpl _context;
 
   /**
    * The object used to access the types from the core library.
    */
   TypeProvider _typeProvider;
@@ skipping 78 matching lines @@
       // resolve
       _resolveReferences(rootNode);
       _computeConstants(rootNode);
       _resolveErrors = errorListener.getErrorsForSource(_source);
       // verify
       _verify(rootNode);
       _context.invalidateLibraryHints(_librarySource);
       _generateLints(rootNode);
       // update entry errors
       _updateEntry();
-      // notify library
-      _definingLibrary.afterIncrementalResolution();
+      // notify unit
+      _definingUnit.afterIncrementalResolution();
       // OK
       return true;
     } finally {
       logger.exit();
     }
   }
 
   void _buildElements(AstNode node) {
     LoggingTimer timer = logger.startTimer();
     try {
@@ skipping 941 matching lines @@
   @override
   String toString() => name;
 }
 
 class _TokenPair {
   final _TokenDifferenceKind kind;
   final Token oldToken;
   final Token newToken;
   _TokenPair(this.kind, this.oldToken, this.newToken);
 }