rename completion source files to match content

pkg/analysis_server/lib/src/services/completion/dart_completion_manager.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 services.completion.dart;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart';
-import 'package:analysis_server/src/services/completion/arglist_computer.dart';
-import 'package:analysis_server/src/services/completion/combinator_computer.dart';
+import 'package:analysis_server/src/services/completion/arglist_contributor.dart';
+import 'package:analysis_server/src/services/completion/combinator_contributor.dart';
 import 'package:analysis_server/src/services/completion/common_usage_computer.dart';
 import 'package:analysis_server/src/services/completion/completion_manager.dart';
 import 'package:analysis_server/src/services/completion/completion_target.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_cache.dart';
-import 'package:analysis_server/src/services/completion/imported_computer.dart';
-import 'package:analysis_server/src/services/completion/invocation_computer.dart';
-import 'package:analysis_server/src/services/completion/keyword_computer.dart';
-import 'package:analysis_server/src/services/completion/local_computer.dart';
+import 'package:analysis_server/src/services/completion/imported_reference_contributor.dart';
+import 'package:analysis_server/src/services/completion/prefixed_element_contributor.dart';
+import 'package:analysis_server/src/services/completion/keyword_contributor.dart';
+import 'package:analysis_server/src/services/completion/local_reference_contributor.dart';
 import 'package:analysis_server/src/services/completion/optype.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 const int DART_RELEVANCE_COMMON_USAGE = 1200;
 const int DART_RELEVANCE_DEFAULT = 1000;
 const int DART_RELEVANCE_HIGH = 2000;
@@ skipping 343 matching lines @@
             parameterNames: suggestion.parameterNames,
             parameterTypes: suggestion.parameterTypes,
             requiredParameterCount: suggestion.requiredParameterCount,
             hasNamedParameters: suggestion.hasNamedParameters,
             returnType: suggestion.returnType,
             element: suggestion.element);
       }
     }
   }
 }