The element's offset isn't relevant when comparing its dimensions with that of its overflow

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

Index: third_party/WebKit/Source/core/layout/LayoutBox.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBox.cpp b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
index 4fc4b88d0b30ee3b40066ef8b3237f68d14340cc..7e6fa47e78c3b1213081cba605525f99102ee6d8 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -450,22 +450,22 @@ LayoutUnit LayoutBox::clientHeight() const
 
 int LayoutBox::pixelSnappedClientWidth() const
 {
-    return snapSizeToPixel(clientWidth(), location().x() + clientLeft());
+    return snapSizeToPixel(clientWidth(), clientLeft());

[eae, 2016/07/13 20:18:33]

The location is needed to correctly snap the client and offset widths/heights or
it will not match where it is painted.

The width/height does depend on the location. The easiest way to illustrate this
is to imagine a set of repeating inline boxes with a width of 10.5px. Ever other
one will snap to 10px and 11px respectively. This to ensure that the total width
of all of them is as close to (n * 10.5px) as possible.

It is not, however, needed for the overflow rect.

[rhogan, 2016/07/17 18:37:45]

OK, so do we have to live with a scrollbar on this guy?

<div style="top: 87.5px; height: 448.75px; overflow: auto; position: absolute;">
    <div style="height: 449px;">
        <div style="height: 1px; width: 1px;"></div>
    </div>
</div>

 }
 
 int LayoutBox::pixelSnappedClientHeight() const
 {
-    return snapSizeToPixel(clientHeight(), location().y() + clientTop());
+    return snapSizeToPixel(clientHeight(), clientTop());
 }
 
 int LayoutBox::pixelSnappedOffsetWidth(const Element*) const
 {
-    return snapSizeToPixel(offsetWidth(), location().x() + clientLeft());
+    return snapSizeToPixel(offsetWidth(), clientLeft());
 }
 
 int LayoutBox::pixelSnappedOffsetHeight(const Element*) const
 {
-    return snapSizeToPixel(offsetHeight(), location().y() + clientTop());
+    return snapSizeToPixel(offsetHeight(), clientTop());
 }
 
 LayoutUnit LayoutBox::scrollWidth() const
@@ -500,7 +500,7 @@ LayoutUnit LayoutBox::scrollTop() const
 
 int LayoutBox::pixelSnappedScrollWidth() const
 {
-    return snapSizeToPixel(scrollWidth(), location().x() + clientLeft());
+    return snapSizeToPixel(scrollWidth(), clientLeft());
 }
 
 int LayoutBox::pixelSnappedScrollHeight() const
@@ -509,7 +509,7 @@ int LayoutBox::pixelSnappedScrollHeight() const
         return snapSizeToPixel(getScrollableArea()->scrollHeight(), location().y() + clientTop());
     // For objects with visible overflow, this matches IE.
     // FIXME: Need to work right with writing modes.
-    return snapSizeToPixel(scrollHeight(), location().y() + clientTop());
+    return snapSizeToPixel(scrollHeight(), clientTop());
 }
 
 void LayoutBox::setScrollLeft(LayoutUnit newLeft)