Introduce toHTMLInputElement(Node*), and use it.

Source/core/editing/FrameSelection.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 Apple 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 1663 matching lines @@
     // FIXME: Can we provide extentAffinity?
     VisiblePosition visibleStart(range->startPosition(), collapsed ? affinity : DOWNSTREAM);
     VisiblePosition visibleEnd(range->endPosition(), SEL_DEFAULT_AFFINITY);
     setSelection(VisibleSelection(visibleStart, visibleEnd), ClearTypingStyle | (closeTyping ? CloseTyping : 0));
     return true;
 }
 
 bool FrameSelection::isInPasswordField() const
 {
     HTMLTextFormControlElement* textControl = enclosingTextFormControl(start());
-    return textControl && textControl->hasTagName(inputTag) && static_cast<HTMLInputElement*>(textControl)->isPasswordField();
+    return textControl && textControl->hasTagName(inputTag) && toHTMLInputElement(textControl)->isPasswordField();
 }
 
 void FrameSelection::focusedOrActiveStateChanged()
 {
     bool activeAndFocused = isFocusedAndActive();
 
     // Because RenderObject::selectionBackgroundColor() and
     // RenderObject::selectionForegroundColor() check if the frame is active,
     // we have to update places those colors were painted.
     if (RenderView* view = m_frame->document()->renderView())
@@ skipping 373 matching lines @@
     sel.showTreeForThis();
 }
 
 void showTree(const WebCore::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
 }
 
 #endif