rename and improve imported completion computer

pkg/analysis_server/test/domain_completion_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.domain.completion;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/domain_completion.dart';
@@ skipping 121 matching lines @@
     ''');
     return getSuggestions().then((_) {
       expect(replacementOffset, equals(completionOffset));
       expect(replacementLength, equals(0));
       assertHasResult(CompletionSuggestionKind.CLASS, 'Object');
       assertHasResult(CompletionSuggestionKind.CLASS, 'HtmlElement');
       assertNoResult('test');
     });
   }
 
+  test_imports_prefixed() {
+    addTestFile('''
+      import 'dart:html' as foo;
+      main() {^}
+    ''');
+    return getSuggestions().then((_) {
+      expect(replacementOffset, equals(completionOffset));
+      expect(replacementLength, equals(0));
+      assertHasResult(CompletionSuggestionKind.CLASS, 'Object');
+      assertHasResult(CompletionSuggestionKind.LIBRARY_PREFIX, 'foo');
+      assertNoResult('HtmlElement');
+      assertNoResult('test');
+    });
+  }
+
   test_locals() {
     addTestFile('class A {var a; x() {var b;^}}');
     return getSuggestions().then((_) {
       expect(replacementOffset, equals(completionOffset));
       expect(replacementLength, equals(0));
       assertHasResult(CompletionSuggestionKind.CLASS, 'A');
       assertHasResult(CompletionSuggestionKind.FIELD, 'a');
       assertHasResult(CompletionSuggestionKind.VARIABLE, 'b');
       assertHasResult(CompletionSuggestionKind.METHOD_NAME, 'x');
     });
   }
 
   test_topLevel() {
     addTestFile('''
       typedef foo();
       var test = '';
       main() {tes^t}
     ''');
     return getSuggestions().then((_) {
 //      expect(replacementOffset, equals(completionOffset - 3));
 //      expect(replacementLength, equals(4));
       assertHasResult(CompletionSuggestionKind.CLASS, 'Object');
       assertHasResult(CompletionSuggestionKind.TOP_LEVEL_VARIABLE, 'test');
       assertNoResult('HtmlElement');
     });
   }
 }