Cherry-pick r44373, r44378, and r44275.

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 'package:analysis_server/src/analysis_server.dart';
@@ skipping 97 matching lines @@
   void applyChangesToContext(Folder contextFolder, ChangeSet changeSet);
 
   /**
    * We are about to start computing the package map.
    */
   void beginComputePackageMap() {
     // Do nothing.
   }
 
   /**
+   * Compute the set of files that are being flushed, this is defined as
+   * the set of sources in the removed context (context.sources), that are
+   * orphaned by this context being removed (no other context includes this
+   * file.)
+   */
+  List<String> computeFlushedFiles(Folder folder) {
+    AnalysisContext context = _contexts[folder].context;
+    HashSet<String> flushedFiles = new HashSet<String>();
+    for (Source source in context.sources) {
+      flushedFiles.add(source.fullName);
+    }
+    for (_ContextInfo contextInfo in _contexts.values) {
+      AnalysisContext contextN = contextInfo.context;
+      if (context != contextN) {
+        for (Source source in contextN.sources) {
+          flushedFiles.remove(source.fullName);
+        }
+      }
+    }
+    return flushedFiles.toList(growable:false);
+  }
+
+  /**
    * We have finished computing the package map.
    */
   void endComputePackageMap() {
     // Do nothing.
   }
 
   /**
    * Returns `true` if the given absolute [path] is in one of the current
    * root folders and is not excluded.
    */
@@ skipping 606 matching lines @@
     return excludes(resource.path);
   }
 
   /**
    * Returns `true` if [path] is the pubspec file of this context.
    */
   bool isPubspec(String path) {
     return path == pubspecPath;
   }
 }