Issue 23018. Fix for inlining multiline strings with leading whitespaces.

pkg/analyzer/test/generated/ast_test.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.ast_test;
 
 import 'package:analyzer/src/generated/ast.dart';
@@ skipping 1287 matching lines @@
     expect(new SimpleStringLiteral(
         TokenFactory.tokenFromString("'''X'''"), "X").contentsOffset, 3);
     expect(new SimpleStringLiteral(
         TokenFactory.tokenFromString("r'X'"), "X").contentsOffset, 2);
     expect(new SimpleStringLiteral(
         TokenFactory.tokenFromString("r\"X\""), "X").contentsOffset, 2);
     expect(new SimpleStringLiteral(
         TokenFactory.tokenFromString("r\"\"\"X\"\"\""), "X").contentsOffset, 4);
     expect(new SimpleStringLiteral(
         TokenFactory.tokenFromString("r'''X'''"), "X").contentsOffset, 4);
+    // leading whitespace
+    expect(new SimpleStringLiteral(
+        TokenFactory.tokenFromString("''' \ \nX''"), "X").contentsOffset, 6);
+    expect(new SimpleStringLiteral(
+        TokenFactory.tokenFromString('r""" \ \nX"""'), "X").contentsOffset, 7);
   }
 
   void test_isMultiline() {
     expect(new SimpleStringLiteral(
         TokenFactory.tokenFromString("'X'"), "X").isMultiline, isFalse);
     expect(new SimpleStringLiteral(
         TokenFactory.tokenFromString("r'X'"), "X").isMultiline, isFalse);
     expect(new SimpleStringLiteral(
         TokenFactory.tokenFromString("\"X\""), "X").isMultiline, isFalse);
     expect(new SimpleStringLiteral(
@@ skipping 1904 matching lines @@
   static const List<WrapperKind> values = const [
     PREFIXED_LEFT,
     PREFIXED_RIGHT,
     PROPERTY_LEFT,
     PROPERTY_RIGHT,
     NONE
   ];
 
   const WrapperKind(String name, int ordinal) : super(name, ordinal);
 }