Include auto vertical scrollbar in intrinsicScrollbarLogicalWidth.

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

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index 059ae5c56cd837daaecba9df25ae72258ef1403d..2a1ed5c548fb45a4575efdba316d4b0b95b956ad 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -639,6 +639,10 @@ bool PaintLayerScrollableArea::updateAfterLayout(SubtreeLayoutScope* delayedLayo
     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;
@@ -652,21 +656,21 @@ bool PaintLayerScrollableArea::updateAfterLayout(SubtreeLayoutScope* delayedLayo
 
     // 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();
@@ -678,6 +682,11 @@ bool PaintLayerScrollableArea::updateAfterLayout(SubtreeLayoutScope* delayedLayo
         // 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())