Replace custom code by hasOneTextChild API

Source/core/html/HTMLOptionElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2004, 2005, 2006, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2011 Motorola Mobility, Inc.  All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 114 matching lines @@
 {
     RefPtrWillBeRawPtr<Node> protectFromMutationEvents(this);
 
     // Changing the text causes a recalc of a select's items, which will reset the selected
     // index to the first item if the select is single selection with a menu list. We attempt to
     // preserve the selected item.
     RefPtrWillBeRawPtr<HTMLSelectElement> select = ownerSelectElement();
     bool selectIsMenuList = select && select->usesMenuList();
     int oldSelectedIndex = selectIsMenuList ? select->selectedIndex() : -1;
 
     // Handle the common special case where there's exactly 1 child node, and it's a text node.

[adamk, 2014/11/04 00:56:56]

This comment is now very redundant with the code, please remove while you're at
it.

-    Node* child = firstChild();
-    if (child && child->isTextNode() && !child->nextSibling())
-        toText(child)->setData(text);
+    if (hasOneTextChild())
+        toText(firstChild())->setData(text);
     else {
         removeChildren();
         appendChild(Text::create(document(), text), exceptionState);
     }
 
     if (selectIsMenuList && select->selectedIndex() != oldSelectedIndex)
         select->setSelectedIndex(oldSelectedIndex);
 }
 
 void HTMLOptionElement::accessKeyAction(bool)
@@ skipping 262 matching lines @@
         ASSERT(parent);
         if (isHTMLOptGroupElement(*parent)) {
             RenderStyle* parentStyle = parent->renderStyle() ? parent->renderStyle() : parent->computedStyle();
             return !parentStyle || parentStyle->display() == NONE;
         }
     }
     return m_style->display() == NONE;
 }
 
 } // namespace blink