Fix for RenderListBox not showing vertical scrollbar with overlay-scrollbar enabled.

Source/core/rendering/RenderListBox.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  *               2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 209 matching lines @@
     m_scrollToRevealSelectionAfterLayout = false;
 
     int firstIndex = listIndexToRenderListBoxIndex(select->activeSelectionStartListIndex());
     int lastIndex = listIndexToRenderListBoxIndex(select->activeSelectionEndListIndex());
     if (firstIndex >= 0 && !listIndexIsVisible(lastIndex))
         scrollToRevealElementAtListIndexInternal(firstIndex);
 }
 
 void RenderListBox::computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const
 {
-    maxLogicalWidth = m_optionsWidth + 2 * optionsSpacingHorizontal;
-    if (m_vBar)
-        maxLogicalWidth += verticalScrollbarWidth();
+    maxLogicalWidth = m_optionsWidth + 2 * optionsSpacingHorizontal + verticalScrollbarWidth();
     if (!style()->width().isPercent())
         minLogicalWidth = maxLogicalWidth;
 }
 
 void RenderListBox::computePreferredLogicalWidths()
 {
     ASSERT(!m_optionsChanged);
 
     m_minPreferredLogicalWidth = 0;
     m_maxPreferredLogicalWidth = 0;
@@ skipping 139 matching lines @@
         }
     }
 }
 
 int RenderListBox::scrollbarLeft() const
 {
     int scrollbarLeft = 0;
     if (style()->shouldPlaceBlockDirectionScrollbarOnLogicalLeft())
         scrollbarLeft = borderLeft();
     else
-        scrollbarLeft = width() - borderRight() - verticalScrollbarWidth();
+        scrollbarLeft = width() - borderRight() - (m_vBar ? m_vBar->width() : 0);

[tkent, 2014/06/18 04:52:22]

Why isn't this verticalScrollbarWidth()?

[pals, 2014/06/18 05:11:44]

As we see, in case of overlayscrollbars, verticalScrollbarWidth() return 0, so,
in case of "dir: ltr" the scrollbar will be placed at width() [assuming
borderRight() is 0] which at the edge/outside of the Box. So, we will not be
able to see the scrollbar. 

[tkent, 2014/06/18 05:14:42]

Ah, I see. This function calculates the position of scrollbar.
Thanks.

     return scrollbarLeft;
 }
 
 void RenderListBox::paintScrollbar(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     if (m_vBar) {
         IntRect scrollRect = pixelSnappedIntRect(paintOffset.x() + scrollbarLeft(),
             paintOffset.y() + borderTop(),
-            verticalScrollbarWidth(),
+            m_vBar->width(),
             height() - (borderTop() + borderBottom()));
         m_vBar->setFrameRect(scrollRect);
         m_vBar->paint(paintInfo.context, paintInfo.rect);
     }
 }
 
 static LayoutSize itemOffsetForAlignment(TextRun textRun, RenderStyle* itemStyle, Font itemFont, LayoutRect itemBoudingBox)
 {
     ETextAlign actualAlignment = itemStyle->textAlign();
     // FIXME: Firefox doesn't respect JUSTIFY. Should we?
@@ skipping 610 matching lines @@
 {
     return itemBoundingBoxRectInternal(point, listIndexToRenderListBoxIndex(index));
 }
 
 bool RenderListBox::scrollToRevealElementAtListIndex(int index)
 {
     return scrollToRevealElementAtListIndexInternal(listIndexToRenderListBoxIndex(index));
 }
 
 } // namespace WebCore