Use new is*Element() helper functions more in rendering code

Source/core/rendering/RenderButton.cpp

 /**
  * Copyright (C) 2005 Apple Computer, Inc.
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 86 matching lines @@
     innerStyle->setMarginTop(Length());
     innerStyle->setMarginBottom(Length());
     innerStyle->setFlexDirection(style()->flexDirection());
 }
 
 bool RenderButton::canHaveGeneratedChildren() const
 {
     // Input elements can't have generated children, but button elements can. We'll
     // write the code assuming any other button types that might emerge in the future
     // can also have children.
-    return !node()->hasTagName(inputTag);
+    return !isHTMLInputElement(*node());
 }
 
 LayoutRect RenderButton::controlClipRect(const LayoutPoint& additionalOffset) const
 {
     // Clip to the padding box to at least give content the extra padding space.
     return LayoutRect(additionalOffset.x() + borderLeft(), additionalOffset.y() + borderTop(), width() - borderLeft() - borderRight(), height() - borderTop() - borderBottom());
 }
 
 int RenderButton::baselinePosition(FontBaseline baseline, bool firstLine, LineDirectionMode direction, LinePositionMode linePositionMode) const
 {
     ASSERT(linePositionMode == PositionOnContainingLine);
     // We want to call the RenderBlock version of firstLineBoxBaseline to
     // avoid RenderFlexibleBox synthesizing a baseline that we don't want.
     // We use this check as a proxy for "are there any line boxes in this button"
     if (!hasLineIfEmpty() && RenderBlock::firstLineBoxBaseline() == -1) {
         // To ensure that we have a consistent baseline when we have no children,
         // even when we have the anonymous RenderBlock child, we calculate the
         // baseline for the empty case manually here.
         if (direction == HorizontalLine)
             return marginTop() + borderTop() + paddingTop() + contentHeight();
 
         return marginRight() + borderRight() + paddingRight() + contentWidth();
     }
     return RenderFlexibleBox::baselinePosition(baseline, firstLine, direction, linePositionMode);
 }
 
 } // namespace WebCore