Take padding into account during calculation of overflow constraining rect for sticky positioning.

Source/core/rendering/RenderBoxModelObject.cpp

Index: Source/core/rendering/RenderBoxModelObject.cpp
diff --git a/Source/core/rendering/RenderBoxModelObject.cpp b/Source/core/rendering/RenderBoxModelObject.cpp
index b48e46fa3f563c3b63756aed356161944f40261c..bae01cbfebfa2248c829e08f2e9cd5a0a95509ad 100644
--- a/Source/core/rendering/RenderBoxModelObject.cpp
+++ b/Source/core/rendering/RenderBoxModelObject.cpp
@@ -337,6 +337,9 @@ LayoutSize RenderBoxModelObject::stickyPositionOffset() const
     if (enclosingClippingLayer) {
         RenderBox* enclosingClippingBox = toRenderBox(enclosingClippingLayer->renderer());
         LayoutRect clipRect = enclosingClippingBox->overflowClipRect(LayoutPoint());
+        clipRect.move(enclosingClippingBox->paddingLeft(), enclosingClippingBox->paddingTop());
+        clipRect.contract(LayoutSize(enclosingClippingBox->paddingLeft() + enclosingClippingBox->paddingRight(),
+            enclosingClippingBox->paddingTop() + enclosingClippingBox->paddingBottom()));
         constrainingRect = enclosingClippingBox->localToContainerQuad(FloatRect(clipRect), view()).boundingBox();
     } else {
         LayoutRect viewportRect = view()->frameView()->viewportConstrainedVisibleContentRect();