Issue repaints before and after changing the squashing assignment of a RenderLayer.

Source/core/rendering/compositing/CompositedLayerMapping.cpp

Index: Source/core/rendering/compositing/CompositedLayerMapping.cpp
diff --git a/Source/core/rendering/compositing/CompositedLayerMapping.cpp b/Source/core/rendering/compositing/CompositedLayerMapping.cpp
index 3f3eeb5bc620195b3bcd7e04d5f38dbf2058e7f6..38d719bd38f782bc97e01799741a936219085495 100644
--- a/Source/core/rendering/compositing/CompositedLayerMapping.cpp
+++ b/Source/core/rendering/compositing/CompositedLayerMapping.cpp
@@ -2175,10 +2175,12 @@ bool CompositedLayerMapping::updateSquashingLayerAssignment(RenderLayer* squashe
     bool updatedAssignment = false;
     if (nextSquashedLayerIndex < m_squashedLayers.size()) {
         if (!paintInfo.isEquivalentForSquashing(m_squashedLayers[nextSquashedLayerIndex])) {
+            compositor()->repaintOnCompositingChange(squashedLayer);
             updatedAssignment = true;
             m_squashedLayers[nextSquashedLayerIndex] = paintInfo;
         }
     } else {
+        compositor()->repaintOnCompositingChange(squashedLayer);
         m_squashedLayers.append(paintInfo);
         updatedAssignment = true;
     }

[ojan, 2014/06/03 18:41:11]

Nit: you could write this as follows to avoid some minor code duplication:
if (updatedAssignment)
    compositor()->repaintOnCompositingChange(squashedLayer);

[chrishtr, 2014/06/03 20:47:08]

I'm doing it the current way because I want to have it happen before
m_squashedLayers is changed, because in principle that changes compositing
state.