Convert server to use RangeFactory

pkg/analyzer_plugin/test/utilities/range_factory_test.dart

 // Copyright (c) 2017, 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.
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/generated/parser.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer_plugin/utilities/range_factory.dart';
@@ skipping 58 matching lines @@
     SimpleIdentifier mainName = mainFunction.name;
     FunctionBody mainBody = mainFunction.functionExpression.body;
     expect(range.nodes([mainName, mainBody]), new SourceRange(1, 9));
   }
 
   test_nodes_empty() async {
     await resolveTestUnit('main() {}');
     expect(range.nodes([]), new SourceRange(0, 0));
   }
 
+  test_offsetBy() {
+    expect(range.offsetBy(new SourceRange(7, 3), 2), new SourceRange(9, 3));
+  }
+
+  test_offsetEndIndex() {
+    expect(range.offsetEndIndex(6, 11), new SourceRange(6, 5));
+  }
+
   test_startEnd_nodeNode() async {
     await resolveTestUnit(' main() {}');
     FunctionDeclaration mainFunction = testUnit.declarations[0];
     SimpleIdentifier mainName = mainFunction.name;
     FunctionBody mainBody = mainFunction.functionExpression.body;
     expect(range.startEnd(mainName, mainBody), new SourceRange(1, 9));
   }
 
   test_startLength_node() async {
     await resolveTestUnit(' main() {}');
@@ skipping 10 matching lines @@
     expect(range.startStart(mainName, mainBody), new SourceRange(0, 7));
   }
 
   test_token() async {
     await resolveTestUnit(' main() {}');
     FunctionDeclaration mainFunction = testUnit.declarations[0];
     SimpleIdentifier mainName = mainFunction.name;
     expect(range.token(mainName.beginToken), new SourceRange(1, 4));
   }
 }