Make squashing work with subpixel layout

Source/core/rendering/compositing/RenderLayerCompositor.h

Index: Source/core/rendering/compositing/RenderLayerCompositor.h
diff --git a/Source/core/rendering/compositing/RenderLayerCompositor.h b/Source/core/rendering/compositing/RenderLayerCompositor.h
index 00cfd63742939aa73617181c57be9840e8aa9e48..e04c4b203d1649036d1a94ca17b62759b5c23443 100644
--- a/Source/core/rendering/compositing/RenderLayerCompositor.h
+++ b/Source/core/rendering/compositing/RenderLayerCompositor.h
@@ -217,7 +217,7 @@ private:
             , nextSquashedLayerIndex(0)
             , clippingAncestorForMostRecentMapping(0) { }
 
-        void updateSquashingStateForNewMapping(CompositedLayerMappingPtr, bool hasNewCompositedLayerMapping, IntPoint newOffsetFromAbsoluteForSquashingCLM, RenderLayer* clippingAncestorForMostRecentMapping);
+        void updateSquashingStateForNewMapping(CompositedLayerMappingPtr, bool hasNewCompositedLayerMapping, LayoutPoint newOffsetFromAbsoluteForSquashingCLM, RenderLayer* clippingAncestorForMostRecentMapping);
 
         // The most recent composited backing that the layer should squash onto if needed.
         CompositedLayerMappingPtr mostRecentMapping;
@@ -225,7 +225,7 @@ private:
 
         // Absolute coordinates of the compositedLayerMapping's owning layer. This is used for computing the correct
         // positions of renderlayers when they paint into the squashing layer.
-        IntPoint offsetFromAbsoluteForSquashingCLM;
+        LayoutPoint offsetFromAbsoluteForSquashingCLM;
 
         // Counter that tracks what index the next RenderLayer would be if it gets squashed to the current squashing layer.
         size_t nextSquashedLayerIndex;