Fix analysis.getNavigation with the new analysis driver.

pkg/analysis_server/lib/src/domains/analysis/navigation_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.navigation_dart;
 
 import 'package:analysis_server/plugin/analysis/navigation/navigation_core.dart';
 import 'package:analysis_server/src/protocol_server.dart' as protocol;
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 
-NavigationCollector computeSimpleDartNavigation(
-    NavigationCollector collector, CompilationUnit unit) {
+NavigationCollector computeDartNavigation(NavigationCollector collector,
+    CompilationUnit unit, int offset, int length) {
   _DartNavigationCollector dartCollector =
       new _DartNavigationCollector(collector);
   _DartNavigationComputerVisitor visitor =
       new _DartNavigationComputerVisitor(dartCollector);
-  unit.accept(visitor);
+  if (offset == null || length == null) {
+    unit.accept(visitor);
+  } else {
+    AstNode node = _getNodeForRange(unit, offset, length);
+    node?.accept(visitor);
+  }
   return collector;
 }
 
+AstNode _getNodeForRange(CompilationUnit unit, int offset, int length) {
+  AstNode node = new NodeLocator(offset, offset + length).searchWithin(unit);
+  for (AstNode n = node; n != null; n = n.parent) {
+    if (n is Directive) {
+      return n;
+    }
+  }
+  return node;
+}
+
 /**
  * A computer for navigation regions in a Dart [CompilationUnit].
  */
 class DartNavigationComputer implements NavigationContributor {
   @override
   void computeNavigation(NavigationCollector collector, AnalysisContext context,
       Source source, int offset, int length) {
     List<Source> libraries = context.getLibrariesContaining(source);
     if (libraries.isNotEmpty) {
       CompilationUnit unit =
           context.getResolvedCompilationUnit2(source, libraries.first);
       if (unit != null) {
-        _DartNavigationCollector dartCollector =
-            new _DartNavigationCollector(collector);
-        _DartNavigationComputerVisitor visitor =
-            new _DartNavigationComputerVisitor(dartCollector);
-        if (offset == null || length == null) {
-          unit.accept(visitor);
-        } else {
-          AstNode node = _getNodeForRange(unit, offset, length);
-          node?.accept(visitor);
-        }
+        computeDartNavigation(collector, unit, offset, length);
       }
     }
   }
-
-  static AstNode _getNodeForRange(
-      CompilationUnit unit, int offset, int length) {
-    AstNode node = new NodeLocator(offset, offset + length).searchWithin(unit);
-    for (AstNode n = node; n != null; n = n.parent) {
-      if (n is Directive) {
-        return n;
-      }
-    }
-    return node;
-  }
 }
 
 /**
  * A Dart specific wrapper around [NavigationCollector].
  */
 class _DartNavigationCollector {
   final NavigationCollector collector;
 
   _DartNavigationCollector(this.collector);
 
@@ skipping 254 matching lines @@
    */
   void _addUriDirectiveRegion(UriBasedDirective node, Element element) {
     if (element != null) {
       Source source = element.source;
       if (element.context.exists(source)) {
         computer._addRegionForNode(node.uri, element);
       }
     }
   }
 }