Consider subpixel accumulation when invalidating paint

Source/core/rendering/RenderLayerRepainter.cpp

Index: Source/core/rendering/RenderLayerRepainter.cpp
diff --git a/Source/core/rendering/RenderLayerRepainter.cpp b/Source/core/rendering/RenderLayerRepainter.cpp
index a1fa5652aec8f32003aa5485bb3c24d1541fc0b5..af79b5789221de687e65f5e6bf60eef31519aea7 100644
--- a/Source/core/rendering/RenderLayerRepainter.cpp
+++ b/Source/core/rendering/RenderLayerRepainter.cpp
@@ -77,7 +77,7 @@ void RenderLayerRepainter::repaintIncludingNonCompositingDescendants()
 
 void RenderLayerRepainter::repaintIncludingNonCompositingDescendantsInternal(const RenderLayerModelObject* repaintContainer)
 {
-    m_renderer.invalidatePaintUsingContainer(repaintContainer, pixelSnappedIntRect(m_renderer.boundsRectForPaintInvalidation(repaintContainer)), InvalidationLayer);
+    m_renderer.invalidatePaintUsingContainer(repaintContainer, m_renderer.boundsRectForPaintInvalidation(repaintContainer), InvalidationLayer);
 
     // FIXME: Repaints can be issued during style recalc at present, via RenderLayerModelObject::styleWillChange. This happens in scenarios when
     // repaint is needed but not layout.
@@ -124,13 +124,13 @@ void RenderLayerRepainter::setBackingNeedsRepaintInRect(const LayoutRect& r)
             view->repaintViewRectangle(absRect);
         return;
     }
-    IntRect repaintRect = pixelSnappedIntRect(r);
     // FIXME: generalize accessors to backing GraphicsLayers so that this code is squasphing-agnostic.
     if (m_renderer.layer()->groupedMapping()) {
+        // FIXME: how about subpixel accumulation?

[chrishtr, 2014/07/02 04:39:58]

Instead of a non-squashing specific fix, please change this CL to do the
following before line 128:

r.move(renderer()->subpixelAccumulation());


Then you can remove the FIXME and the subpixelAccumulation part of
CompositedLayerMapping.cpp:1928.

[Xianzhu, 2014/07/02 16:19:10]

Thanks for the solution! Done.

         if (GraphicsLayer* squashingLayer = m_renderer.layer()->groupedMapping()->squashingLayer())
-            squashingLayer->setNeedsDisplayInRect(repaintRect);
+            squashingLayer->setNeedsDisplayInRect(pixelSnappedIntRect(r));
     } else {
-        m_renderer.layer()->compositedLayerMapping()->setContentsNeedDisplayInRect(repaintRect);
+        m_renderer.layer()->compositedLayerMapping()->setContentsNeedDisplayInRect(r);
     }
 }