Recompute overflow after transform changes

Source/core/rendering/RenderObject.cpp

Index: Source/core/rendering/RenderObject.cpp
diff --git a/Source/core/rendering/RenderObject.cpp b/Source/core/rendering/RenderObject.cpp
index 277e370252dc96f628c706669070318209422167..34b4e2b846e57d47e1ce2c8a1362fa06d199b611 100644
--- a/Source/core/rendering/RenderObject.cpp
+++ b/Source/core/rendering/RenderObject.cpp
@@ -2112,6 +2112,11 @@ void RenderObject::styleDidChange(StyleDifference diff, const RenderStyle* oldSt
     } else if (diff == StyleDifferenceLayoutPositionedMovementOnly)
         setNeedsPositionedMovementLayout();
 
+    if (!needsLayout() && oldStyle && oldStyle->transform() != m_style->transform()) {
+        if (RenderBlock* container = containingBlock())
+            container->updateOverflowForTransform();

[esprehn, 2014/03/26 02:06:20]

This needs to be async, otherwise if you transform a thousand things you
recompute this a thousand times.

+    }
+
     // Don't check for repaint here; we need to wait until the layer has been
     // updated by subclasses before we know if we have to repaint (in setStyle()).