Support for overlay only files in Analysis Server with the new driver.

pkg/analysis_server/lib/src/context_manager.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.
 
 library context.directory.manager;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:core';
@@ skipping 261 matching lines @@
   List<String> get includedPaths;
 
   /**
    * Return a list of all of the contexts reachable from the given
    * [analysisRoot] (the context associated with [analysisRoot] and all of its
    * descendants).
    */
   List<AnalysisContext> contextsInAnalysisRoot(Folder analysisRoot);
 
   /**
+   * Return the [AnalysisDriver] for the "innermost" context whose associated
+   * folder is or contains the given path.  ("innermost" refers to the nesting
+   * of contexts, so if there is a context for path /foo and a context for
+   * path /foo/bar, then the innermost context containing /foo/bar/baz.dart is
+   * the context for /foo/bar.)
+   *
+   * If no driver contains the given path, `null` is returned.
+   */
+  AnalysisDriver getDriverFor(String path);
+
+  /**
    * Return the [AnalysisContext] for the "innermost" context whose associated
    * folder is or contains the given path.  ("innermost" refers to the nesting
    * of contexts, so if there is a context for path /foo and a context for
    * path /foo/bar, then the innermost context containing /foo/bar/baz.dart is
    * the context for /foo/bar.)
    *
    * If no context contains the given path, `null` is returned.
    */
   AnalysisContext getContextFor(String path);
 
@@ skipping 284 matching lines @@
     }
     return contexts;
   }
 
   /**
    * Check if this map defines embedded libraries.
    */
   bool definesEmbeddedLibs(Map map) => map[_EMBEDDED_LIB_MAP_KEY] != null;
 
   @override
+  AnalysisDriver getDriverFor(String path) {
+    return _getInnermostContextInfoFor(path)?.analysisDriver;
+  }
+
+  @override
   AnalysisContext getContextFor(String path) {
     return _getInnermostContextInfoFor(path)?.context;
   }
 
   /**
    * For testing: get the [ContextInfo] object for the given [folder], if any.
    */
   ContextInfo getContextInfoFor(Folder folder) {
     ContextInfo info = _getInnermostContextInfoFor(folder.path);
     if (info != null && folder == info.folder) {
@@ skipping 1350 matching lines @@
     }
     return _embedderLocator;
   }
 
   @override
   SdkExtensionFinder getSdkExtensionFinder(ResourceProvider resourceProvider) {
     return _sdkExtensionFinder ??=
         new SdkExtensionFinder(buildPackageMap(resourceProvider));
   }
 }