Make RenderObject::style() return a const object

Source/core/layout/LayoutTextControl.cpp

 /**
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  *           (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * 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,
@@ skipping 54 matching lines @@
 void LayoutTextControl::styleDidChange(StyleDifference diff, const LayoutStyle* oldStyle)
 {
     RenderBlockFlow::styleDidChange(diff, oldStyle);
     Element* innerEditor = innerEditorElement();
     if (!innerEditor)
         return;
     RenderBlock* innerEditorRenderer = toRenderBlock(innerEditor->renderer());
     if (innerEditorRenderer) {
         // We may have set the width and the height in the old style in layout().
         // Reset them now to avoid getting a spurious layout hint.
-        innerEditorRenderer->style()->setHeight(Length());
-        innerEditorRenderer->style()->setWidth(Length());
+        innerEditorRenderer->mutableStyle()->setHeight(Length());
+        innerEditorRenderer->mutableStyle()->setWidth(Length());
         innerEditorRenderer->setStyle(createInnerEditorStyle(styleRef()));
         innerEditor->setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::Control));
     }
     textFormControlElement()->updatePlaceholderVisibility(false);
 }
 
 static inline void updateUserModifyProperty(HTMLTextFormControlElement& node, LayoutStyle& style)
 {
     style.setUserModify(node.isDisabledOrReadOnly() ? READ_ONLY : READ_WRITE_PLAINTEXT_ONLY);
 }
@@ skipping 207 matching lines @@
     HTMLElement* placeholder = toHTMLTextFormControlElement(node())->placeholderElement();
     LayoutObject* placeholderRenderer = placeholder ? placeholder->renderer() : 0;
     if (!placeholderRenderer)
         return 0;
     if (relayoutChildren)
         layoutScope.setChildNeedsLayout(placeholderRenderer);
     return placeholderRenderer;
 }
 
 } // namespace blink