improve keyword suggestions when completing partial keyword

pkg/analysis_server/test/services/completion/keyword_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.dart.keyword;
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/completion/keyword_computer.dart';
 import 'package:analysis_testing/reflective_tests.dart';
 import 'package:analyzer/src/generated/scanner.dart';
@@ skipping 127 matching lines @@
             'abstract',
             'class',
             'const',
             'export',
             'final',
             'import',
             'part',
             'typedef',
             'var']);
   }
+
+  test_partial_class() {
+    addTestSource('cl^');
+    expect(computeFast(), isTrue);
+    assertSuggestKeywords(
+        [
+            'abstract',
+            'class',
+            'const',
+            'export',
+            'final',
+            'import',
+            'library',
+            'part',
+            'typedef',
+            'var']);
+  }
+
+  test_partial_class2() {
+    addTestSource('library a; cl^');
+    expect(computeFast(), isTrue);
+    assertSuggestKeywords(
+        [
+            'abstract',
+            'class',
+            'const',
+            'export',
+            'final',
+            'import',
+            'part',
+            'typedef',
+            'var']);
+  }
 }