Add a getNavigation request for plugins

pkg/analyzer_plugin/lib/plugin/plugin.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 'dart:async';
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart'
     show AnalysisDriverGeneric, AnalysisDriverScheduler;
@@ skipping 174 matching lines @@
     return null;
   }
 
   /**
    * Create an analysis driver that can analyze the files within the given
    * [contextRoot].
    */
   AnalysisDriverGeneric createAnalysisDriver(ContextRoot contextRoot);
 
   /**
+   * Handle an 'analysis.getNavigation' request.
+   */
+  Future<AnalysisGetNavigationResult> handleAnalysisGetNavigation(
+      AnalysisGetNavigationParams params) async {
+    return new AnalysisGetNavigationResult(
+        <String>[], <NavigationTarget>[], <NavigationRegion>[]);
+  }
+
+  /**
    * Handle an 'analysis.handleWatchEvents' request.
    */
   Future<AnalysisHandleWatchEventsResult> handleAnalysisHandleWatchEvents(
       AnalysisHandleWatchEventsParams parameters) async {
     for (WatchEvent event in parameters.events) {
       switch (event.type) {
         case WatchEventType.ADD:
           // TODO(brianwilkerson) Handle the event.
           break;
         case WatchEventType.MODIFY:
@@ skipping 280 matching lines @@
     }
   }
 
   /**
    * Compute the response that should be returned for the given [request], or
    * `null` if the response has already been sent.
    */
   Future<Response> _getResponse(Request request, int requestTime) async {
     ResponseResult result = null;
     switch (request.method) {
+      case ANALYSIS_REQUEST_GET_NAVIGATION:
+        var params = new AnalysisGetNavigationParams.fromRequest(request);
+        result = await handleAnalysisGetNavigation(params);
+        break;
       case ANALYSIS_REQUEST_HANDLE_WATCH_EVENTS:
         var params = new AnalysisHandleWatchEventsParams.fromRequest(request);
         result = await handleAnalysisHandleWatchEvents(params);
         break;
       case ANALYSIS_REQUEST_REANALYZE:
         var params = new AnalysisReanalyzeParams.fromRequest(request);
         result = await handleAnalysisReanalyze(params);
         break;
       case ANALYSIS_REQUEST_SET_CONTEXT_BUILDER_OPTIONS:
         var params =
@@ skipping 71 matching lines @@
       response = new Response(id, requestTime,
           error: new RequestError(
               RequestErrorCode.PLUGIN_ERROR, exception.toString(),
               stackTrace: stackTrace.toString()));
     }
     if (response != null) {
       _channel.sendResponse(response);
     }
   }
 }