Implement 'analysis.occurrences' for the new analysis driver.

pkg/analysis_server/lib/src/domains/analysis/occurrences_dart.dart

 // Copyright (c) 2015, 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 domains.analysis.occurrences_dart;
 
 import 'package:analysis_server/plugin/analysis/occurrences/occurrences_core.dart';
 import 'package:analysis_server/src/protocol_server.dart' as protocol;
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/member.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 
+void addDartOccurrences(OccurrencesCollector collector, CompilationUnit unit) {
+  _DartUnitOccurrencesComputerVisitor visitor =
+      new _DartUnitOccurrencesComputerVisitor();
+  unit.accept(visitor);
+  visitor.elementsOffsets.forEach((engineElement, offsets) {
+    int length = engineElement.nameLength;
+    protocol.Element serverElement = protocol.convertElement(engineElement);
+    protocol.Occurrences occurrences =
+        new protocol.Occurrences(serverElement, offsets, length);
+    collector.addOccurrences(occurrences);
+  });
+}
+
 /**
  * A computer for occurrences in a Dart [CompilationUnit].
  */
 class DartOccurrencesComputer implements OccurrencesContributor {
   @override
   void computeOccurrences(
       OccurrencesCollector collector, AnalysisContext context, Source source) {
     List<Source> libraries = context.getLibrariesContaining(source);
     if (libraries.isNotEmpty) {
       CompilationUnit unit =
           context.getResolvedCompilationUnit2(source, libraries.first);
       if (unit != null) {
-        _DartUnitOccurrencesComputerVisitor visitor =
-            new _DartUnitOccurrencesComputerVisitor();
-        unit.accept(visitor);
-        visitor.elementsOffsets.forEach((engineElement, offsets) {
-          int length = engineElement.nameLength;
-          protocol.Element serverElement =
-              protocol.convertElement(engineElement);
-          protocol.Occurrences occurrences =
-              new protocol.Occurrences(serverElement, offsets, length);
-          collector.addOccurrences(occurrences);
-        });
+        addDartOccurrences(collector, unit);
       }
     }
   }
 }
 
 class _DartUnitOccurrencesComputerVisitor extends RecursiveAstVisitor {
   final Map<Element, List<int>> elementsOffsets = <Element, List<int>>{};
 
   @override
   visitSimpleIdentifier(SimpleIdentifier node) {
@@ skipping 23 matching lines @@
     }
     if (element is PropertyAccessorElement) {
       element = (element as PropertyAccessorElement).variable;
     }
     if (element is Member) {
       element = (element as Member).baseElement;
     }
     return element;
   }
 }