Remove unnecessary casts and general code clean-up

pkg/analyzer/lib/src/task/incremental_element_builder.dart

 // Copyright (c) 2015, 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 analyzer.src.task.incremental_element_builder;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 285 matching lines @@
         break;
       }
       oldToken = oldToken.next;
       newToken = newToken.next;
     }
   }
 
   static Token getBeginTokenNotComment(AstNode node) {
     Token oldBeginToken = node.beginToken;
     if (oldBeginToken is CommentToken) {
-      oldBeginToken = (oldBeginToken as CommentToken).parent;
+      return oldBeginToken.parent;
     }
     return oldBeginToken;
   }
 
   /**
    * Return the token string of all the [node] tokens.
    */
   static String getFullCode(AstNode node) {
     List<Token> tokens = getTokens(node);
     return joinTokens(tokens);
@@ skipping 46 matching lines @@
     }
     int oldOffset = element.nameOffset;
     int newOffset = map[oldOffset];
     assert(newOffset != null);
     (element as ElementImpl).nameOffset = newOffset;
     if (element is! LibraryElement) {
       super.visitElement(element);
     }
   }
 }