Use ContainerNode::hasChildren() instead of firstChild() in conditionals

Source/core/html/shadow/DateTimeEditElement.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 644 matching lines @@
 }
 
 bool DateTimeEditElement::isReadOnly() const
 {
     return m_editControlOwner && m_editControlOwner->isEditControlOwnerReadOnly();
 }
 
 void DateTimeEditElement::layout(const LayoutParameters& layoutParameters, const DateComponents& dateValue)
 {
     DEFINE_STATIC_LOCAL(AtomicString, fieldsWrapperPseudoId, ("-webkit-datetime-edit-fields-wrapper", AtomicString::ConstructFromLiteral));
-    if (!firstChild()) {
+    if (!hasChildren()) {
         RefPtrWillBeRawPtr<HTMLDivElement> element = HTMLDivElement::create(document());
         element->setShadowPseudoId(fieldsWrapperPseudoId);
         appendChild(element.get());
     }
     Element* fieldsWrapper = fieldsWrapperElement();
 
     size_t focusedFieldIndex = this->focusedFieldIndex();
     DateTimeFieldElement* const focusedField = fieldAt(focusedFieldIndex);
     const AtomicString focusedFieldId = focusedField ? focusedField->shadowPseudoId() : nullAtom;
 
@@ skipping 132 matching lines @@
 {
     DateTimeFieldsState dateTimeFieldsState;
     for (size_t fieldIndex = 0; fieldIndex < m_fields.size(); ++fieldIndex)
         m_fields[fieldIndex]->populateDateTimeFieldsState(dateTimeFieldsState);
     return dateTimeFieldsState;
 }
 
 } // namespace blink
 
 #endif