Integration of MOVE_FILE into the server and a couple of fixes.

pkg/analysis_server/test/services/refactoring/move_file_test.dart

Index: pkg/analysis_server/test/services/refactoring/move_file_test.dart
diff --git a/pkg/analysis_server/test/services/refactoring/move_file_test.dart b/pkg/analysis_server/test/services/refactoring/move_file_test.dart
index f9c7e9cf3f11a4d66d300cc9098725d4e7537f03..9437e5d8b52673465c0a817b96991fb36e1473c8 100644
--- a/pkg/analysis_server/test/services/refactoring/move_file_test.dart
+++ b/pkg/analysis_server/test/services/refactoring/move_file_test.dart
@@ -38,6 +38,7 @@ class MoveFileTest extends RefactoringTest {
     addSource(pathD, '');
     addTestSource('''
 library lib;
+import 'dart:math';
 import '22/c.dart';
 export '333/d.dart';
 part 'a.dart';
@@ -52,6 +53,7 @@ part '/absolute/uri.dart';
       assertNoFileChange(pathC);
       assertFileChangeResult(testFile, '''
 library lib;
+import 'dart:math';
 import 'c.dart';
 export '../333/d.dart';
 part '../a.dart';