improve keyword suggestions

pkg/analysis_server/lib/src/services/completion/dart_completion_manager.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;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/completion/completion_manager.dart';
@@ skipping 55 matching lines @@
   }
 
   /**
    * Compute suggestions based upon cached information only
    * then send an initial response to the client.
    */
   void computeFast() {
     CompilationUnit unit = context.parseCompilationUnit(source);
     request.unit = unit;
     request.node = new NodeLocator.con1(offset).searchWithin(unit);
-    if (request.node != null) {
-      request.node.accept(new _ReplacementOffsetBuilder(request));
-    }
+    request.node.accept(new _ReplacementOffsetBuilder(request));
     computers.removeWhere((DartCompletionComputer c) => c.computeFast(request));
     sendResults(computers.isEmpty);
   }
 
   /**
    * If there is remaining work to be done, then wait for the unit to be
    * resolved and request that each remaining computer finish their work.
    */
   void computeFull() {
     waitForAnalysis().then((CompilationUnit unit) {
@@ skipping 134 matching lines @@
   _ReplacementOffsetBuilder(this.request) {
     request.replacementOffset = request.offset;
     request.replacementLength = 0;
   }
 
   visitSimpleIdentifier(SimpleIdentifier node) {
     request.replacementOffset = node.offset;
     request.replacementLength = node.length;
   }
 }