CSS4: Implement :placeholder-shown pseudo class

Source/core/html/HTMLTextFormControlElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2009, 2010, 2011 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 41 matching lines @@
     };
 
     ~HTMLTextFormControlElement() override;
 
     void forwardEvent(Event*);
 
 
     InsertionNotificationRequest insertedInto(ContainerNode*) override;
 
     // The derived class should return true if placeholder processing is needed.
+    virtual bool isPlaceholderVisible() const = 0;
+    virtual void setPlaceholderVisibility(bool) = 0;
     virtual bool supportsPlaceholder() const = 0;
     String strippedPlaceholder() const;
-    bool placeholderShouldBeVisible() const;
     HTMLElement* placeholderElement() const;
-    void updatePlaceholderVisibility(bool);
+    void updatePlaceholderVisibility();
 
     VisiblePosition visiblePositionForIndex(int) const;
     int indexForVisiblePosition(const VisiblePosition&) const;
     int selectionStart() const;
     int selectionEnd() const;
     const AtomicString& selectionDirection() const;
     void setSelectionStart(int);
     void setSelectionEnd(int);
     void setSelectionDirection(const String&);
     void select(NeedToDispatchSelectEvent = DispatchSelectEvent);
@@ skipping 69 matching lines @@
 
     // Returns true if user-editable value is empty. Used to check placeholder visibility.
     virtual bool isEmptyValue() const = 0;
     // Returns true if suggested value is empty. Used to check placeholder visibility.
     virtual bool isEmptySuggestedValue() const { return true; }
     // Called in dispatchFocusEvent(), after placeholder process, before calling parent's dispatchFocusEvent().
     virtual void handleFocusEvent(Element* /* oldFocusedNode */, WebFocusType) { }
     // Called in dispatchBlurEvent(), after placeholder process, before calling parent's dispatchBlurEvent().
     virtual void handleBlurEvent() { }
 
+    bool placeholderShouldBeVisible() const;
+
     String m_textAsOfLastFormControlChangeEvent;
     bool m_lastChangeWasUserEdit;
 
     int m_cachedSelectionStart;
     int m_cachedSelectionEnd;
     TextFieldSelectionDirection m_cachedSelectionDirection;
 };
 
 inline bool isHTMLTextFormControlElement(const Element& element)
 {
     return element.isTextFormControl();
 }
 
 DEFINE_HTMLELEMENT_TYPE_CASTS_WITH_FUNCTION(HTMLTextFormControlElement);
 
 HTMLTextFormControlElement* enclosingTextFormControl(const Position&);
 HTMLTextFormControlElement* enclosingTextFormControl(Node*);
 
 } // namespace
 
 #endif