[repaint-after-layout] Only repaint SVG root element when needed.

Source/core/rendering/svg/RenderSVGRoot.cpp

 /*
  * Copyright (C) 2004, 2005, 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2007, 2008, 2009 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Google, Inc.
  * Copyright (C) Research In Motion Limited 2011. 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 177 matching lines @@
         return document().frame()->ownerRenderer()->availableLogicalHeight(IncludeMarginBorderPadding);
 
     // SVG embedded via SVGImage (background-image/border-image/etc) / Inline SVG.
     return RenderReplaced::computeReplacedLogicalHeight();
 }
 
 void RenderSVGRoot::layout()
 {
     ASSERT(needsLayout());
 
-    LayoutRectRecorder recorder(*this);
-
     // Arbitrary affine transforms are incompatible with LayoutState.
     LayoutStateDisabler layoutStateDisabler(*this);
 
     bool needsLayout = selfNeedsLayout();
+    LayoutRectRecorder recorder(*this, !(checkForRepaint() && needsLayout));

[esprehn, 2014/03/21 18:17:29]

Can you propagate the ! through the statement? It's much easier to read that
way.

!checkForRepaint() || !needsLayout()

[dsinclair, 2014/03/24 14:46:28]

The flag was badly named, so I inverted the meaning and made this just
checkForRepaint() && needsLayout()

     LayoutRepainter repainter(*this, checkForRepaintDuringLayout() && needsLayout);
 
     LayoutSize oldSize = size();
     updateLogicalWidth();
     updateLogicalHeight();
     buildLocalToBorderBoxTransform();
 
     SVGRenderSupport::layoutResourcesIfNeeded(this);
 
     SVGSVGElement* svg = toSVGSVGElement(node());
@@ skipping 228 matching lines @@
 
 bool RenderSVGRoot::hasRelativeLogicalHeight() const
 {
     SVGSVGElement* svg = toSVGSVGElement(node());
     ASSERT(svg);
 
     return svg->intrinsicHeight(SVGSVGElement::IgnoreCSSProperties).isPercent();
 }
 
 }