refactor library prefix suggestion generation

pkg/analysis_server/test/services/completion/imported_computer_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.services.completion.toplevel;
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/completion/imported_computer.dart';
 import 'package:unittest/unittest.dart';
 
@@ skipping 35 matching lines @@
       class X {foo(){^}}''');
     // pass true for full analysis to pick up unimported source
     return computeFull(true).then((_) {
       assertSuggestClass('A');
       assertNotSuggested('x');
       assertNotSuggested('_B');
       assertSuggestClass('C');
       assertNotSuggested('D');
       assertSuggestClass('EE');
       assertNotSuggested('F');
-      // Don't suggest library prefix as it is suggested by local computer
-      // TODO (danrubel) modify so that imported_computer handles
-      // all aspects of import statement
-      assertNotSuggested('g');
+      assertSuggestLibraryPrefix('g');
       assertNotSuggested('G');
       assertSuggestClass('H', CompletionRelevance.LOW);
       // Should not suggest compilation unit elements
       // which are returned by the LocalComputer
       assertNotSuggested('X');
       assertSuggestClass('Object');
       // TODO (danrubel) suggest HtmlElement as low relevance
       assertNotSuggested('HtmlElement');
     });
   }
@@ skipping 219 matching lines @@
     return computeFull().then((_) {
       assertSuggestClass('A');
       assertNotSuggested('x');
       assertNotSuggested('_B');
       // Should not suggest compilation unit elements
       // which are returned by the LocalComputer
       assertNotSuggested('C');
     });
   }
 }