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 d5dfa279e43f7722398d7af39a0c67016f61c87c..109268ce6200f80c0db9196e7778737d769d1dc6 100644
--- a/Source/core/rendering/RenderBoxModelObject.cpp
+++ b/Source/core/rendering/RenderBoxModelObject.cpp
@@ -344,6 +344,9 @@ LayoutSize RenderBoxModelObject::stickyPositionOffset() const
     if (enclosingClippingLayer) {
         RenderBox* enclosingClippingBox = toRenderBox(enclosingClippingLayer->renderer());
         LayoutRect clipRect = enclosingClippingBox->overflowClipRect(LayoutPoint(), 0); // FIXME: make this work in regions.
+        clipRect.move(enclosingClippingBox->paddingLeft(), enclosingClippingBox->paddingTop());

[ojan, 2014/02/19 20:03:24]

The equivalent webkit patch didn't have this
(https://bugs.webkit.org/attachment.cgi?id=224328&action=review). Can you
explain why this is needed?

[ostap, 2014/02/19 20:50:00]

Webkit takes padding into account for the position in
computeStickyPositionConstraints() .
That's because of this commit: http://trac.webkit.org/changeset/152998 
I don't think this change is relevant for chromium.

+        clipRect.contract(LayoutSize(enclosingClippingBox->paddingLeft() + enclosingClippingBox->paddingRight(),
+            enclosingClippingBox->paddingTop() + enclosingClippingBox->paddingBottom()));
         constrainingRect = enclosingClippingBox->localToContainerQuad(FloatRect(clipRect), view()).boundingBox();
     } else {
         LayoutRect viewportRect = view()->frameView()->viewportConstrainedVisibleContentRect();