Make server use the common protocol classes

pkg/analysis_server/test/integration/analysis/occurrences_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.
 
 import 'package:analysis_server/protocol/protocol_generated.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../support/integration_tests.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(OccurrencesTest);
   });
 }
@@ skipping 42 matching lines @@
         Set<int> foundOffsets = findOffsets(elementName);
         expect(foundOffsets, equals(expectedOffsets));
       }
 
       check('i', ['i = 0', 'i < 10', 'i++', 'i;']);
       check('j', ['j = 0', 'j < i', 'j++', 'j;']);
       check('sum', ['sum = 0', 'sum +=', 'sum)']);
     });
   }
 }