Remove timeStamp from the ChangeBuilder API

pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart

Index: pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart
diff --git a/pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart b/pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart
index c0e7ae08b602c7c36ce67a2f546616a36af670f3..16bd03415f9d90c83f811dde80d802cd9a5f1900 100644
--- a/pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart
+++ b/pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart
@@ -40,15 +40,15 @@ class DartChangeBuilderImpl extends ChangeBuilderImpl
   DartChangeBuilderImpl(this.driver);
 
   @override
-  Future<Null> addFileEdit(String path, int fileStamp,
-          void buildFileEdit(DartFileEditBuilder builder)) =>
-      super.addFileEdit(path, fileStamp, buildFileEdit);
+  Future<Null> addFileEdit(
+          String path, void buildFileEdit(DartFileEditBuilder builder)) =>
+      super.addFileEdit(path, buildFileEdit);
 
   @override
-  Future<DartFileEditBuilderImpl> createFileEditBuilder(
-      String path, int fileStamp) async {
+  Future<DartFileEditBuilderImpl> createFileEditBuilder(String path) async {
     AnalysisResult result = await driver.getResult(path);
-    return new DartFileEditBuilderImpl(this, path, fileStamp, result.unit);
+    int timeStamp = driver.fsState.getFileForPath(path).exists ? 0 : -1;
+    return new DartFileEditBuilderImpl(this, path, timeStamp, result.unit);
   }
 }