Conditionally create PaintLayer's scrollable area object

third_party/WebKit/Source/core/layout/svg/LayoutSVGBlock.cpp

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) Research In Motion Limited 2010. 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
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 17 matching lines @@
 #include "core/style/ShadowList.h"
 #include "core/svg/SVGElement.h"
 
 namespace blink {
 
 LayoutSVGBlock::LayoutSVGBlock(SVGElement* element)
     : LayoutBlockFlow(element)
 {
 }
 
-void LayoutSVGBlock::updateFromStyle()
+bool LayoutSVGBlock::allowsOverflowClip() const
 {
-    LayoutBlock::updateFromStyle();
-
-    // LayoutSVGlock, used by Layout(SVGText|ForeignObject), is not allowed to call setHasOverflowClip(true).
+    // LayoutSVGlock, used by Layout(SVGText|ForeignObject), is not allowed to have overflow clip.
     // LayoutBlock assumes a layer to be present when the overflow clip functionality is requested. Both
     // Layout(SVGText|ForeignObject) return 'NoPaintLayer' on 'layerTypeRequired'. Fine for LayoutSVGText.
     //
     // If we want to support overflow rules for <foreignObject> we can choose between two solutions:
     // a) make LayoutSVGForeignObject require layers and SVG layer aware
     // b) reactor overflow logic out of Layer (as suggested by dhyatt), which is a large task
     //
     // Until this is resolved, disable overflow support. Opera/FF don't support it as well at the moment (Feb 2010).
     //
     // Note: This does NOT affect overflow handling on outer/inner <svg> elements - this is handled
     // manually by LayoutSVGRoot - which owns the documents enclosing root layer and thus works fine.
-    setHasOverflowClip(false);
+    return false;
 }
 
 void LayoutSVGBlock::absoluteRects(Vector<IntRect>&, const LayoutPoint&) const
 {
     // This code path should never be taken for SVG, as we're assuming useTransforms=true everywhere, absoluteQuads should be used.
     ASSERT_NOT_REACHED();
 }
 
 void LayoutSVGBlock::willBeDestroyed()
 {
@@ skipping 50 matching lines @@
 void LayoutSVGBlock::invalidateTreeIfNeeded(PaintInvalidationState& paintInvalidationState)
 {
     if (!shouldCheckForPaintInvalidation(paintInvalidationState))
         return;
 
     ForceHorriblySlowRectMapping slowRectMapping(&paintInvalidationState);
     LayoutBlockFlow::invalidateTreeIfNeeded(paintInvalidationState);
 }
 
 } // namespace blink