Update the plugin API

pkg/analyzer_plugin/lib/utilities/navigation/navigation.dart

 // Copyright (c) 2017, 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.
 
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer_plugin/protocol/protocol.dart';
 import 'package:analyzer_plugin/protocol/protocol_common.dart'
     show ElementKind, Location;
 import 'package:analyzer_plugin/protocol/protocol_generated.dart';
 import 'package:analyzer_plugin/src/utilities/navigation/navigation.dart';
 import 'package:analyzer_plugin/utilities/generator.dart';
 
 /**
+ * The information about a requested set of navigation information when
+ * computing navigation information in a `.dart` file.
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+abstract class DartNavigationRequest implements NavigationRequest {
+  /**
+   * The analysis result for the file in which the navigation regions are being
+   * requested.
+   */
+  ResolveResult get result;
+}
+
+/**
  * An object that [NavigationContributor]s use to record navigation regions.
  *
  * Clients may not extend, implement or mix-in this class.
  */
 abstract class NavigationCollector {
   /**
    * Record a new navigation region with the given [offset] and [length] that
    * should navigate to the given [targetLocation].
    */
   void addRegion(
@@ skipping 42 matching lines @@
     for (NavigationContributor contributor in contributors) {
       try {
         contributor.computeNavigation(request, collector);
       } catch (exception, stackTrace) {
         notifications.add(new PluginErrorParams(
                 false, exception.toString(), stackTrace.toString())
             .toNotification());
       }
     }
     collector.createRegions();
-    notifications.add(new AnalysisNavigationParams(request.result.path,
-            collector.regions, collector.targets, collector.files)
+    notifications.add(new AnalysisNavigationParams(
+            request.path, collector.regions, collector.targets, collector.files)
         .toNotification());
     return new GeneratorResult(null, notifications);
   }
 
   /**
    * Create an 'analysis.getNavigation' response for the portion of the file
    * specified by the given [request]. If any of the contributors throws an
    * exception, also create a non-fatal 'plugin.error' notification.
    */
   GeneratorResult generateNavigationResponse(NavigationRequest request) {
@@ skipping 27 matching lines @@
    */
   int get length;
 
   /**
    * Return the offset of the region within the source for which navigation
    * regions are being requested.
    */
   int get offset;
 
   /**
+   * Return the path of the file in which navigation regions are being requested.
+   */
+  String get path;
+
+  /**
    * Return the resource provider associated with this request.
    */
   ResourceProvider get resourceProvider;
-
-  /**
-   * The analysis result for the file in which the navigation regions are being
-   * requested.
-   */
-  ResolveResult get result;
 }