Add Autofill preview support for <select> input fields

public/web/WebFormControlElement.h

 /*
  * 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 55 matching lines @@
 
     // Returns true if autocomplete attribute of the element is not set as "off".
     BLINK_EXPORT bool autoComplete() const;
 
     // Sets value for input element, textarea element and select element. For select
     // element it finds the option with value matches the given parameter and make the
     // option as the current selection.
     BLINK_EXPORT void setValue(const WebString&, bool sendChangeEvent = false);
     // Returns value of element. For select element, it returns the value of
     // the selected option if present. If no selected option, an empty string
-    // is returned. For any other types of elements, a null string is returned.
+    // is returned. If element doesn't fall into input element, textarea element
+    // and select element categories, a null string is returned.
     BLINK_EXPORT WebString value() const;
-    // Sets suggested value for element. The goal of introducing suggested value
-    // is to not leak any information to JavaScript.
+    // Sets suggested value for element. For select element it finds the option
+    // with value matches the given parameter and make the option as the suggested
+    // selection. The goal of introducing suggested value is to not leak any information
+    // to JavaScript.
     BLINK_EXPORT void setSuggestedValue(const WebString&);
-    // Returns suggested value for input element or textarea element. If neither
-    // input element nor textarea element, a null string is returned.
+    // Returns suggested value of element. If element doesn't fall into input element,
+    // textarea element and select element categories, a null string is returned.
     BLINK_EXPORT WebString suggestedValue() const;
 
     // Returns the non-sanitized, exact value inside the text input field
     // or insisde the textarea. If neither input element nor textarea element,
     // a null string is returned.
     BLINK_EXPORT WebString editingValue() const;
 
     // Sets character selection range.
     BLINK_EXPORT void setSelectionRange(int start, int end);
     // Returned value represents a cursor/caret position at the current
@@ skipping 18 matching lines @@
 #if BLINK_IMPLEMENTATION
     WebFormControlElement(const WTF::PassRefPtr<WebCore::HTMLFormControlElement>&);
     WebFormControlElement& operator=(const WTF::PassRefPtr<WebCore::HTMLFormControlElement>&);
     operator WTF::PassRefPtr<WebCore::HTMLFormControlElement>() const;
 #endif
 };
 
 } // namespace blink
 
 #endif