Disable overlay scrollbars to hide them on non-Mac.

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 2445 matching lines @@
 }
 
 bool FrameView::scrollbarsCanBeActive() const {
   if (m_frame->view() != this)
     return false;
 
   return !!m_frame->document();
 }
 
 void FrameView::scrollbarVisibilityChanged() {
+  updateScrollbarEnabledState();
   LayoutViewItem viewItem = layoutViewItem();
   if (!viewItem.isNull())
     viewItem.clearHitTestCache();
 }
 
 IntRect FrameView::scrollableAreaBoundingBox() const {
   LayoutPartItem ownerLayoutItem = frame().ownerLayoutItem();
   if (ownerLayoutItem.isNull())
     return frameRect();
 
@@ skipping 1341 matching lines @@
       (option == FirstPass && docSize.width() <= fullVisibleSize.width() &&
        docSize.height() <= fullVisibleSize.height());
   if (attemptToRemoveScrollbars) {
     if (hScroll == ScrollbarAuto)
       newHasHorizontalScrollbar = false;
     if (vScroll == ScrollbarAuto)
       newHasVerticalScrollbar = false;
   }
 }
 
+void FrameView::updateScrollbarEnabledState() {
+  bool forceDisabled =
+      ScrollbarTheme::theme().shouldDisableInvisibleScrollbars() &&
+      scrollbarsHidden();
+
+  if (horizontalScrollbar()) {
+    horizontalScrollbar()->setEnabled(contentsWidth() > visibleWidth() &&
+                                      !forceDisabled);
+  }
+  if (verticalScrollbar()) {
+    verticalScrollbar()->setEnabled(contentsHeight() > visibleHeight() &&
+                                    !forceDisabled);
+  }
+}
+
 void FrameView::updateScrollbarGeometry() {
+  updateScrollbarEnabledState();
   if (horizontalScrollbar()) {
     int thickness = horizontalScrollbar()->scrollbarThickness();
-    int clientWidth = visibleWidth();
     IntRect oldRect(horizontalScrollbar()->frameRect());
     IntRect hBarRect(
         (shouldPlaceVerticalScrollbarOnLeft() && verticalScrollbar())
             ? verticalScrollbar()->width()
             : 0,
         height() - thickness,
         width() - (verticalScrollbar() ? verticalScrollbar()->width() : 0),
         thickness);
     horizontalScrollbar()->setFrameRect(hBarRect);
     if (oldRect != horizontalScrollbar()->frameRect())
       setScrollbarNeedsPaintInvalidation(HorizontalScrollbar);
 
-    horizontalScrollbar()->setEnabled(contentsWidth() > clientWidth);
-    horizontalScrollbar()->setProportion(clientWidth, contentsWidth());
+    horizontalScrollbar()->setProportion(visibleWidth(), contentsWidth());
     horizontalScrollbar()->offsetDidChange();
   }
 
   if (verticalScrollbar()) {
     int thickness = verticalScrollbar()->scrollbarThickness();
-    int clientHeight = visibleHeight();
     IntRect oldRect(verticalScrollbar()->frameRect());
     IntRect vBarRect(
         shouldPlaceVerticalScrollbarOnLeft() ? 0 : (width() - thickness), 0,
         thickness,
         height() -
             (horizontalScrollbar() ? horizontalScrollbar()->height() : 0));
     verticalScrollbar()->setFrameRect(vBarRect);
     if (oldRect != verticalScrollbar()->frameRect())
       setScrollbarNeedsPaintInvalidation(VerticalScrollbar);
 
-    verticalScrollbar()->setEnabled(contentsHeight() > clientHeight);
-    verticalScrollbar()->setProportion(clientHeight, contentsHeight());
+    verticalScrollbar()->setProportion(visibleHeight(), contentsHeight());
     verticalScrollbar()->offsetDidChange();
   }
 }
 
 bool FrameView::adjustScrollbarExistence(
     ComputeScrollbarExistenceOption option) {
   ASSERT(m_inUpdateScrollbars);
 
   // If we came in here with the view already needing a layout, then go ahead
   // and do that first.  (This will be the common case, e.g., when the page
@@ skipping 740 matching lines @@
   DCHECK(m_frame->isMainFrame());
   return m_initialViewportSize.width();
 }
 
 int FrameView::initialViewportHeight() const {
   DCHECK(m_frame->isMainFrame());
   return m_initialViewportSize.height();
 }
 
 }  // namespace blink