extract LibraryMemberContributor from prefixed element contributor

pkg/analysis_server/test/services/completion/completion_test_util.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.services.completion.util;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart' as protocol
     show Element, ElementKind;
@@ skipping 3967 matching lines @@
       class Y { }''');
     addTestSource('''
       import "/testB.dart" as b;
       var T2;
       class A { }
       main() {b.^}''');
     computeFast();
     return computeFull((bool result) {
       expect(request.replacementOffset, completionOffset);
       expect(request.replacementLength, 0);
-      assertSuggestInvocationClass('X');
-      assertSuggestInvocationClass('Y');
-      assertSuggestInvocationTopLevelVar('T1', null);
+      // Suggested by LibraryMemberContributor
+      assertNotSuggested('X');
+      assertNotSuggested('Y');
+      assertNotSuggested('T1');
       assertNotSuggested('T2');
       assertNotSuggested('Object');
       assertNotSuggested('b');
       assertNotSuggested('A');
       assertNotSuggested('==');
     });
   }
 
   test_PrefixedIdentifier_library_typesOnly() {
     // SimpleIdentifier  PrefixedIdentifier  TypeName
     addSource(
         '/testB.dart',
         '''
       lib B;
       var T1;
       class X { }
       class Y { }''');
     addTestSource('''
       import "/testB.dart" as b;
       var T2;
       class A { }
       foo(b.^ f) {}''');
     computeFast();
     return computeFull((bool result) {
       expect(request.replacementOffset, completionOffset);
       expect(request.replacementLength, 0);
-      assertSuggestInvocationClass('X');
-      assertSuggestInvocationClass('Y');
+      // Suggested by LibraryMemberContributor
+      assertNotSuggested('X');
+      assertNotSuggested('Y');
       assertNotSuggested('T1');
       assertNotSuggested('T2');
       assertNotSuggested('Object');
       assertNotSuggested('b');
       assertNotSuggested('A');
       assertNotSuggested('==');
     });
   }
 
   test_PrefixedIdentifier_library_typesOnly2() {
     // SimpleIdentifier  PrefixedIdentifier  TypeName
     addSource(
         '/testB.dart',
         '''
       lib B;
       var T1;
       class X { }
       class Y { }''');
     addTestSource('''
       import "/testB.dart" as b;
       var T2;
       class A { }
       foo(b.^) {}''');
     computeFast();
     return computeFull((bool result) {
       expect(request.replacementOffset, completionOffset);
       expect(request.replacementLength, 0);
-      assertSuggestInvocationClass('X');
-      assertSuggestInvocationClass('Y');
+      // Suggested by LibraryMemberContributor
+      assertNotSuggested('X');
+      assertNotSuggested('Y');
       assertNotSuggested('T1');
       assertNotSuggested('T2');
       assertNotSuggested('Object');
       assertNotSuggested('b');
       assertNotSuggested('A');
       assertNotSuggested('==');
     });
   }
 
   test_PrefixedIdentifier_parameter() {
@@ skipping 638 matching lines @@
       assertNotSuggested('bar2');
       assertNotSuggested('_B');
       assertSuggestLocalClass('Y');
       assertSuggestLocalClass('C');
       assertSuggestLocalVariable('f', null);
       assertNotSuggested('x');
       assertNotSuggested('e');
     });
   }
 }