Reset m_didTransformToRootUpdate flag during invalidationTreeIfNeeded

Source/core/rendering/svg/RenderSVGTransformableContainer.h

 /*
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Google, 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,
@@ skipping 17 matching lines @@
 class SVGGraphicsElement;
 class RenderSVGTransformableContainer FINAL : public RenderSVGContainer {
 public:
     explicit RenderSVGTransformableContainer(SVGGraphicsElement*);
 
     virtual bool isChildAllowed(RenderObject*, RenderStyle*) const OVERRIDE;
 
     virtual bool isSVGTransformableContainer() const OVERRIDE { return true; }
     virtual const AffineTransform& localToParentTransform() const OVERRIDE { return m_localTransform; }
     virtual void setNeedsTransformUpdate() OVERRIDE { m_needsTransformUpdate = true; }
-    virtual bool didTransformToRootUpdate() OVERRIDE { return m_didTransformToRootUpdate; }
+    virtual bool didTransformToRootUpdate() const OVERRIDE { return m_didTransformToRootUpdate; }

[Julien - ping for review, 2014/07/23 18:47:39]

m_didTransformToRoot is reset during layout (RenderSVGContainer::layout()) so it
seems pretty weird for us to have to do something here.

More conceptually, we may trigger several layouts before producing a frame that
will generate invalidation so it's unclear to me:
A) what this tries to achieve.
B) why this is correct if subsequent layouts could have cleared the flag before
we generate an invalidation.

[Xianzhu, 2014/07/23 18:52:29]

I think you are right. Perhaps we should not clear the flag during layout.

fs@opera.com, wdyt?

[Xianzhu, 2014/07/23 19:05:08]

The latest Patch Set avoids resetting the flag during layout.

+    virtual void clearPaintInvalidationState() OVERRIDE;
 
 private:
     virtual bool calculateLocalTransform() OVERRIDE;
     virtual AffineTransform localTransform() const OVERRIDE { return m_localTransform; }
 
+#if ENABLE(ASSERT)
+    virtual bool paintInvalidationStateIsDirty() const OVERRIDE  { return RenderSVGContainer::paintInvalidationStateIsDirty() || m_didTransformToRootUpdate; }
+#endif
+
     bool m_needsTransformUpdate : 1;
     bool m_didTransformToRootUpdate : 1;
     AffineTransform m_localTransform;
     FloatSize m_lastTranslation;
 };
 
 }
 
 #endif // RenderSVGTransformableContainer_h