Set scrollbar enabled state for overflow:auto.

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>
@@ skipping 639 matching lines @@
 
 void PaintLayerScrollableArea::updateScrollDimensions() {
   if (m_overflowRect.size() != box().layoutOverflowRect().size())
     contentsResized();
   m_overflowRect = box().layoutOverflowRect();
   box().flipForWritingMode(m_overflowRect);
   updateScrollOrigin();
 }
 
 void PaintLayerScrollableArea::updateScrollbarEnabledState() {
-  bool forceDisabled = ScrollbarTheme::theme().disableInvisibleScrollbars() &&
-                       scrollbarsHidden();
-  // overflow:scroll should just enable/disable.
-  if (box().style()->overflowX() == OverflowScroll && horizontalScrollbar()) {
-    horizontalScrollbar()->setEnabled(hasHorizontalOverflow() &&
-                                      !forceDisabled);
-  }
-  if (box().style()->overflowY() == OverflowScroll && verticalScrollbar()) {
-    verticalScrollbar()->setEnabled(hasVerticalOverflow() && !forceDisabled);
-  }
+  bool forceDisable = ScrollbarTheme::theme().disableInvisibleScrollbars() &&
+                      scrollbarsHidden();
+
+  if (horizontalScrollbar())
+    horizontalScrollbar()->setEnabled(hasHorizontalOverflow() && !forceDisable);
+  if (verticalScrollbar())
+    verticalScrollbar()->setEnabled(hasVerticalOverflow() && !forceDisable);
 }
 
 void PaintLayerScrollableArea::setScrollOffsetUnconditionally(
     const ScrollOffset& offset,
     ScrollType scrollType) {
   cancelScrollAnimation();
   scrollOffsetChanged(offset, scrollType);
 }
 
 void PaintLayerScrollableArea::updateAfterLayout() {
@@ skipping 1298 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     clampScrollableAreas() {
   for (auto& scrollableArea : *s_needsClamp)
     scrollableArea->clampScrollOffsetsAfterLayout();
   delete s_needsClamp;
   s_needsClamp = nullptr;
 }
 
 }  // namespace blink