Update ChangeBuilder to the new driver

pkg/analysis_server/lib/src/provisional/edit/utilities/change_builder_core.dart

Index: pkg/analysis_server/lib/src/provisional/edit/utilities/change_builder_core.dart
diff --git a/pkg/analysis_server/lib/src/provisional/edit/utilities/change_builder_core.dart b/pkg/analysis_server/lib/src/provisional/edit/utilities/change_builder_core.dart
index 8c357433bbe276abfcfbf2365ce05ff20dc521da..8fbcbdf48989e1921b96f3ba6565d65c06e69e68 100644
--- a/pkg/analysis_server/lib/src/provisional/edit/utilities/change_builder_core.dart
+++ b/pkg/analysis_server/lib/src/provisional/edit/utilities/change_builder_core.dart
@@ -2,11 +2,10 @@
 // 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 analysis_server.plugin.edit.utilities.change_builder_core;
+import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/utilities/change_builder_core.dart';
-import 'package:analyzer/src/generated/source.dart';
 
 /**
  * A builder used to build a [SourceChange].
@@ -20,18 +19,20 @@ abstract class ChangeBuilder {
   factory ChangeBuilder() = ChangeBuilderImpl;
 
   /**
-   * Return the source change that was built.
+   * Return the source change that was built. The source change will not be
+   * complete until all of the futures returned by [addFileEdit] have completed.

[scheglov, 2017/02/08 21:09:10]

Maybe this getter should return a Future that completes when all addFileEdit()
invocations are complete. So, there would be no way for the clients to make a
mistake. I guess most of them will wait for addFileEdit() anyway, but maybe not.

[Brian Wilkerson, 2017/02/09 03:22:42]

I considered that, and I'm still not completely convinced either way. If we
returned a Future here we could presumably *not* return a Future from
addFileEdit. At least, I don't think there's a reason to have both.

    */
   SourceChange get sourceChange;
 
   /**
    * Use the [buildFileEdit] function to create a collection of edits to the
-   * given [source]. The edits will be added to the source change that is being
-   * built. The [timeStamp] is the time at which the [source] was last modified
-   * and is used by clients to ensure that it is safe to apply the edits.
+   * file with the given [path]. The edits will be added to the source change
+   * that is being built. The [timeStamp] is the time at which the file was last
+   * modified and is used by clients to ensure that it is safe to apply the
+   * edits.
    */
-  void addFileEdit(Source source, int timeStamp,
-      void buildFileEdit(FileEditBuilder builder));
+  Future<Null> addFileEdit(
+      String path, int timeStamp, void buildFileEdit(FileEditBuilder builder));

[scheglov, 2017/02/08 21:09:10]

BTW, I think that ideally we should migrate from timestamps to content MD5s.

[Brian Wilkerson, 2017/02/09 03:22:42]

I'm not sure we want to require clients to compute MD5 hashes of files. In any
case, not in this CL.

 }
 
 /**