Include auto vertical scrollbar in intrinsicScrollbarLogicalWidth.

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 621 matching lines @@
         // PaintLayerScrollableArea does not maintain that flag: it gets set, but it never
         // gets unset.  We should unset the flag after layout.
         scrollPositionChanged(scrollPositionDouble(), ProgrammaticScroll);
     }
 
     m_scrollbarManager.setCanDetachScrollbars(false);
 
     bool hasHorizontalOverflow = this->hasHorizontalOverflow();
     bool hasVerticalOverflow = this->hasVerticalOverflow();
 
+    // Don't add auto scrollbars if the box contents aren't visible.
+    bool shouldHaveAutoHorizontalScrollbar = hasHorizontalOverflow && box().pixelSnappedClientHeight();
+    bool shouldHaveAutoVerticalScrollbar = hasVerticalOverflow && box().pixelSnappedClientWidth();
+
     {
         // Hits in compositing/overflow/automatically-opt-into-composited-scrolling-after-style-change.html.
         DisableCompositingQueryAsserts disabler;
 
         // overflow:scroll should just enable/disable.
         if (box().style()->overflowX() == OverflowScroll && horizontalScrollbar())
             horizontalScrollbar()->setEnabled(hasHorizontalOverflow);
         if (box().style()->overflowY() == OverflowScroll && verticalScrollbar())
             verticalScrollbar()->setEnabled(hasVerticalOverflow);
     }
 
     // We need to layout again if scrollbars are added or removed by overflow:auto,
     // or by changing between native and custom.
-    bool horizontalScrollBarChanged = (box().hasAutoHorizontalScrollbar() && (hasHorizontalScrollbar() != hasHorizontalOverflow))
+    bool horizontalScrollBarChanged = (box().hasAutoHorizontalScrollbar() && (hasHorizontalScrollbar() != shouldHaveAutoHorizontalScrollbar))
         || (box().style()->overflowX() == OverflowScroll && !horizontalScrollbar());
-    bool verticalScrollBarChanged = (box().hasAutoVerticalScrollbar() && (hasVerticalScrollbar() != hasVerticalOverflow))
+    bool verticalScrollBarChanged = (box().hasAutoVerticalScrollbar() && (hasVerticalScrollbar() != shouldHaveAutoVerticalScrollbar))
         || (box().style()->overflowY() == OverflowScroll && !verticalScrollbar());
     if (!visualViewportSuppliesScrollbars() && (horizontalScrollBarChanged || verticalScrollBarChanged)) {
         if (box().hasAutoHorizontalScrollbar())
-            setHasHorizontalScrollbar(hasHorizontalOverflow);
+            setHasHorizontalScrollbar(shouldHaveAutoHorizontalScrollbar);
         else if (box().style()->overflowX() == OverflowScroll)
             setHasHorizontalScrollbar(true);
         if (box().hasAutoVerticalScrollbar())
-            setHasVerticalScrollbar(hasVerticalOverflow);
+            setHasVerticalScrollbar(shouldHaveAutoVerticalScrollbar);
         else if (box().style()->overflowY() == OverflowScroll)
             setHasVerticalScrollbar(true);
 
-        if (hasVerticalOverflow || hasHorizontalOverflow)
+        if (hasScrollbar())
             updateScrollCornerStyle();
 
         layer()->updateSelfPaintingLayer();
 
         // Force an update since we know the scrollbars have changed things.
         if (box().document().hasAnnotatedRegions())
             box().document().setAnnotatedRegionsDirty(true);
 
         // Our proprietary overflow: overlay value doesn't trigger a layout.
         if ((horizontalScrollBarChanged && box().style()->overflowX() != OverflowOverlay) || (verticalScrollBarChanged && box().style()->overflowY() != OverflowOverlay)) {
             if (!m_inOverflowRelayout) {
+                if ((verticalScrollBarChanged && box().isHorizontalWritingMode())
+                    || (horizontalScrollBarChanged && !box().isHorizontalWritingMode())) {
+                    box().setPreferredLogicalWidthsDirty();
+                    box().updateLogicalWidth();

[skobes, 2016/05/16 20:55:53]

Won't this (updateLogicalWidth) happen during layout anyway?

[szager1, 2016/05/23 22:17:31]

If delayedLayoutScope is not null, then layout won't necessarily run again right
away, but the logical width still needs to be correct for the parent.  I can
move updateLogicalWidth() into the delayedLayoutScope clause.

+                }
                 m_inOverflowRelayout = true;
                 if (delayedLayoutScope) {
                     if (box().isLayoutBlock())
                         toLayoutBlock(box()).scrollbarsChanged(horizontalScrollBarChanged, verticalScrollBarChanged);
                     delayedLayoutScope->setNeedsLayout(&box(), LayoutInvalidationReason::ScrollbarChanged);
                     didMarkForDelayedLayout = true;
                 } else {
                     SubtreeLayoutScope layoutScope(box());
                     layoutScope.setNeedsLayout(&box(), LayoutInvalidationReason::ScrollbarChanged);
                     if (box().isLayoutBlock()) {
@@ skipping 917 matching lines @@
 }
 
 DEFINE_TRACE(PaintLayerScrollableArea::ScrollbarManager)
 {
     visitor->trace(m_scrollableArea);
     visitor->trace(m_hBar);
     visitor->trace(m_vBar);
 }
 
 } // namespace blink