Store repaint rects in the coordinate space of their backing GraphicsLayer.

Source/core/rendering/RenderLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 333 matching lines @@
 
     bool hasCompositedMask() const;
     bool hasCompositedClippingMask() const;
     bool needsCompositedScrolling() const { return m_scrollableArea && m_scrollableArea->needsCompositedScrolling(); }
 
     bool clipsCompositingDescendantsWithBorderRadius() const;
 
     RenderLayer* scrollParent() const;
     RenderLayer* clipParent() const;
 
+    // Adjusts the given rect to the coordinate space of the repaint container's GraphicsLayer backing.
+    void computeRectForRepaint(const RenderLayerModelObject* repaintContainer, LayoutRect&) const;

[leviw_travelin_and_unemployed, 2014/05/29 18:27:08]

These 2 functions are really confusing... Can we come up with names that don't
force me to read the comments to know what they do?

It doesn't seem like this function is really computing the rect for repaint.
It's mapping a provided rect to a coordinate space. Is the rect passed in
already clipped?

[chrishtr, 2014/05/29 18:34:11]

The function is agnostic to the rect's purpose. It's just a dirty rect. Agree
about naming. Changed.
Seems better?

+
+    // Computes the bounding repaint rect for this layer, in the coordinate space of the repaint container's GraphicsLayer backing.
+    LayoutRect computeRepaintRect(const RenderLayerModelObject* repaintContainer) const;
+
     bool needsCompositingLayersRebuiltForClip(const RenderStyle* oldStyle, const RenderStyle* newStyle) const;
     bool needsCompositingLayersRebuiltForOverflow(const RenderStyle* oldStyle, const RenderStyle* newStyle) const;
     bool needsCompositingLayersRebuiltForFilters(const RenderStyle* oldStyle, const RenderStyle* newStyle) const;
     bool needsCompositingLayersRebuiltForBlending(const RenderStyle* oldStyle, const RenderStyle* newStyle) const;
 
     bool paintsWithTransparency(PaintBehavior paintBehavior) const
     {
         return isTransparent() && ((paintBehavior & PaintBehaviorFlattenCompositingLayers) || compositingState() != PaintsIntoOwnBacking);
     }
 
@@ skipping 385 matching lines @@
 
 } // namespace WebCore
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const WebCore::RenderLayer*);
 void showLayerTree(const WebCore::RenderObject*);
 #endif
 
 #endif // RenderLayer_h