Update composited layer size if overflow from children requires it

third_party/WebKit/Source/core/layout/LayoutBlock.cpp

Index: third_party/WebKit/Source/core/layout/LayoutBlock.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBlock.cpp b/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
index 3d33a0af551508f5a92e8b69b0f9512036ecabc4..860274f46a39d989823c745a4d2850ce83358c18 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBlock.cpp
@@ -438,8 +438,12 @@ void LayoutBlock::computeOverflow(LayoutUnit oldClientAfterEdge, bool)
     }
 
     addVisualEffectOverflow();
-
     addVisualOverflowFromTheme();
+
+    // An enclosing composited layer will need to update its bounds if we now overflow it.
+    PaintLayer* layer = enclosingLayer();
+    if (!needsLayout() && layer->hasCompositedLayerMapping() && !layer->visualRect().contains(visualOverflowRect()))
+        layer->setNeedsCompositingInputsUpdate();
 }
 
 void LayoutBlock::addOverflowFromBlockChildren()