Issue 24277. Use node's offset as the source range start for the first unit node in Outline.

pkg/analysis_server/test/analysis/notification_outline_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.
 
 library test.analysis.notification.outline;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/protocol.dart';
@@ skipping 559 matching lines @@
           int end = testCode.indexOf(" // marker2");
           expect(outline.offset, offset);
           expect(outline.length, end - offset);
         }
       }
     });
   }
 
   test_sourceRange_inUnit() {
     addTestFile('''
+library lib;
+/// My first class.
 class A {
 } // endA
 class B {
 } // endB
 ''');
     return prepareOutline().then((_) {
       Outline unitOutline = outline;
       List<Outline> topOutlines = unitOutline.children;
       expect(topOutlines, hasLength(2));
       // A
       {
         Outline outline = topOutlines[0];
         Element element = outline.element;
         expect(element.kind, ElementKind.CLASS);
         expect(element.name, "A");
         {
-          int offset = 0;
+          int offset = testCode.indexOf("/// My first class.");
           int end = testCode.indexOf(" // endA");
           expect(outline.offset, offset);
           expect(outline.length, end - offset);
         }
       }
       // B
       {
         Outline outline = topOutlines[1];
         Element element = outline.element;
         expect(element.kind, ElementKind.CLASS);
@@ skipping 203 matching lines @@
   }
 
   void _isEnumConstant(Outline outline, String name) {
     Element element = outline.element;
     expect(element.kind, ElementKind.ENUM_CONSTANT);
     expect(element.name, name);
     expect(element.parameters, isNull);
     expect(element.returnType, isNull);
   }
 }