Add Autofill preview support for <select> input fields

Source/web/WebFormControlElement.cpp

 /*
  * Copyright (C) 2010 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 101 matching lines @@
         return constUnwrap<HTMLSelectElement>()->value();
     return WebString();
 }
 
 void WebFormControlElement::setSuggestedValue(const WebString& value)
 {
     if (isHTMLInputElement(*m_private))
         unwrap<HTMLInputElement>()->setSuggestedValue(value);
     if (isHTMLTextAreaElement(*m_private))
         unwrap<HTMLTextAreaElement>()->setSuggestedValue(value);
+    if (isHTMLSelectElement(*m_private))
+        unwrap<HTMLSelectElement>()->setSuggestedValue(value);
 }
 
 WebString WebFormControlElement::suggestedValue() const
 {
     if (isHTMLInputElement(*m_private))
         return constUnwrap<HTMLInputElement>()->suggestedValue();
     if (isHTMLTextAreaElement(*m_private))
         return constUnwrap<HTMLTextAreaElement>()->suggestedValue();
+    if (isHTMLSelectElement(*m_private))
+        return constUnwrap<HTMLSelectElement>()->suggestedValue();
     return WebString();
 }
 
 WebString WebFormControlElement::editingValue() const
 {
     if (isHTMLInputElement(*m_private))
         return constUnwrap<HTMLInputElement>()->innerTextValue();
     if (isHTMLTextAreaElement(*m_private))
         return constUnwrap<HTMLTextAreaElement>()->innerTextValue();
     return WebString();
@@ skipping 49 matching lines @@
     m_private = elem;
     return *this;
 }
 
 WebFormControlElement::operator PassRefPtr<HTMLFormControlElement>() const
 {
     return toHTMLFormControlElement(m_private.get());
 }
 
 } // namespace blink