Fix a recent regression with nested contexts

pkg/analysis_server/lib/src/analysis_server.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.
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:core';
 import 'dart:io' as io;
 import 'dart:math' show max;
 
@@ skipping 668 matching lines @@
     }
     return null;
   }
 
   /**
    * Return an analysis driver to which the file with the given [path] is
    * added if one exists, otherwise a driver in which the file was analyzed if
    * one exists, otherwise the first driver, otherwise `null`.
    */
   nd.AnalysisDriver getAnalysisDriver(String path) {
-    Iterable<nd.AnalysisDriver> drivers = driverMap.values;
+    List<nd.AnalysisDriver> drivers = driverMap.values.toList();
     if (drivers.isNotEmpty) {
+      // Sort the drivers so that more deeply nested contexts will be checked
+      // before enclosing contexts.
+      drivers.sort((first, second) =>
+          second.contextRoot.root.length - first.contextRoot.root.length);
       nd.AnalysisDriver driver = drivers.firstWhere(
           (driver) => driver.contextRoot.containsFile(path),
           orElse: () => null);
       driver ??= drivers.firstWhere(
           (driver) => driver.knownFiles.contains(path),
           orElse: () => null);
       driver ??= drivers.first;
       return driver;
     }
     return null;
@@ skipping 1663 matching lines @@
   /**
    * The [PerformanceTag] for time spent in server request handlers.
    */
   static PerformanceTag serverRequests = new PerformanceTag('serverRequests');
 
   /**
    * The [PerformanceTag] for time spent in split store microtasks.
    */
   static PerformanceTag splitStore = new PerformanceTag('splitStore');
 }