Don't paint below image's baseline unless it is selected.

Source/core/rendering/RenderReplaced.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009 Apple Inc. 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 51 matching lines @@
     virtual void styleDidChange(StyleDifference, const RenderStyle* oldStyle) OVERRIDE;
 
     void setIntrinsicSize(const LayoutSize& intrinsicSize) { m_intrinsicSize = intrinsicSize; }
     virtual void intrinsicSizeChanged();
 
     virtual void paint(PaintInfo&, const LayoutPoint&) OVERRIDE;
     bool shouldPaint(PaintInfo&, const LayoutPoint&);
     LayoutRect localSelectionRect(bool checkWhetherSelected = true) const; // This is in local coordinates, but it's a physical rect (so the top left corner is physical top left).
     virtual RenderBox* embeddedContentBox() const { return 0; }
 
+    virtual LayoutRect overflowRectForRepaint() const OVERRIDE FINAL { return isSelected() ? localSelectionRect() : visualOverflowRect(); }

[Julien - ping for review, 2014/05/02 00:23:35]

I wonder if it would make sense for the visualOverflowRect to just include the
selection rect. The downside of that would be that you would need to recompute
it whenever selection changes but I think it's an OK trade off.

Also is this change really required as it seems orthogonal to the fix which
would be the computeRepaintRect when changing the selection state?

[rhogan, 2014/05/02 15:36:27]

That's what we do currently for replaced objects - paint the union of the
selection rect and the overflow rect. That's unnecessary invalidation unless the
image is selected. If it isn't selected we just want to invalidate the
visualOverflowRect() - which is the motivation of this change.
The call to computeRepaintRects() when changing selection state is required in
order to keep the cached repaint rect up to date for images with a layer. Images
without a layer get it when they need it from overflowRectForRepaint().

+
 private:
     virtual const char* renderName() const OVERRIDE { return "RenderReplaced"; }
 
     virtual bool canHaveChildren() const OVERRIDE { return false; }
 
     virtual void computePreferredLogicalWidths() OVERRIDE FINAL;
     virtual void paintReplaced(PaintInfo&, const LayoutPoint&) { }
 
-    virtual LayoutRect clippedOverflowRectForRepaint(const RenderLayerModelObject* repaintContainer) const OVERRIDE;
-
     virtual PositionWithAffinity positionForPoint(const LayoutPoint&) OVERRIDE FINAL;
 
     virtual bool canBeSelectionLeaf() const OVERRIDE { return true; }
 
     virtual LayoutRect selectionRectForRepaint(const RenderLayerModelObject* repaintContainer, bool clipToVisibleContent = true) OVERRIDE FINAL;
     void computeAspectRatioInformationForRenderBox(RenderBox*, FloatSize& constrainedSize, double& intrinsicRatio) const;
 
     mutable LayoutSize m_intrinsicSize;
 };
 
 }
 
 #endif