Fix for highlighting 'abstract' in ClassTypeAlias.

pkg/analysis_server/lib/src/computer/computer_highlights.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 computer.highlights;
 
 import 'package:analysis_server/src/protocol.dart' hide Element;
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/scanner.dart';
@@ skipping 365 matching lines @@
   @override
   Object visitClassDeclaration(ClassDeclaration node) {
     computer._addRegion_token(node.classKeyword, HighlightRegionType.KEYWORD);
     computer._addRegion_token(
         node.abstractKeyword,
         HighlightRegionType.BUILT_IN);
     return super.visitClassDeclaration(node);
   }
 
   @override
+  Object visitClassTypeAlias(ClassTypeAlias node) {
+    computer._addRegion_token(
+        node.abstractKeyword,
+        HighlightRegionType.BUILT_IN);
+    return super.visitClassTypeAlias(node);
+  }
+
+  @override
   Object visitConstructorDeclaration(ConstructorDeclaration node) {
     computer._addRegion_token(
         node.externalKeyword,
         HighlightRegionType.BUILT_IN);
     computer._addRegion_token(
         node.factoryKeyword,
         HighlightRegionType.BUILT_IN);
     return super.visitConstructorDeclaration(node);
   }
 
@@ skipping 261 matching lines @@
     computer._addRegion_token(node.keyword, HighlightRegionType.KEYWORD);
     return super.visitWhileStatement(node);
   }
 
   @override
   Object visitWithClause(WithClause node) {
     computer._addRegion_token(node.withKeyword, HighlightRegionType.KEYWORD);
     return super.visitWithClause(node);
   }
 }