Implement overlay scrollbar fade out for non-composited scrollers.

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 152 matching lines @@
           box().document().rootScrollerController())
     controller->didDisposePaintLayerScrollableArea(*this);
 
   m_scrollbarManager.dispose();
 
   if (m_scrollCorner)
     m_scrollCorner->destroy();
   if (m_resizer)
     m_resizer->destroy();
 
-  clearScrollAnimators();
+  clearScrollableArea();
 
   // Note: it is not safe to call ScrollAnchor::clear if the document is being
   // destroyed, because LayoutObjectChildList::removeChildNode skips the call to
   // willBeRemovedFromTree,
   // leaving the ScrollAnchor with a stale LayoutObject pointer.
   if (RuntimeEnabledFeatures::scrollAnchoringEnabled() &&
       !box().documentBeingDestroyed())
     m_scrollAnchor.clearSelf();
 
 #if ENABLE(ASSERT)
@@ skipping 175 matching lines @@
       maximumScrollOffsetInt() - minimumScrollOffsetInt();
   return (orientation == HorizontalScrollbar) ? scrollDimensions.width()
                                               : scrollDimensions.height();
 }
 
 void PaintLayerScrollableArea::updateScrollOffset(const ScrollOffset& newOffset,
                                                   ScrollType scrollType) {
   if (scrollOffset() == newOffset)
     return;
 
+  showOverlayScrollbars();
   ScrollOffset scrollDelta = scrollOffset() - newOffset;
   m_scrollOffset = newOffset;
 
   LocalFrame* frame = box().frame();
   ASSERT(frame);
 
   FrameView* frameView = box().frameView();
 
   TRACE_EVENT1("devtools.timeline", "ScrollLayer", "data",
                InspectorScrollLayerEvent::data(&box()));
@@ skipping 129 matching lines @@
             : 0;
   }
 
   // TODO(szager): Handle fractional scroll offsets correctly.
   return IntRect(
       flooredIntPoint(scrollPosition()),
       IntSize(max(0, layer()->size().width() - verticalScrollbarWidth),
               max(0, layer()->size().height() - horizontalScrollbarHeight)));
 }
 
+void PaintLayerScrollableArea::visibleContentResized() {
+  showOverlayScrollbars();
+}
+
 int PaintLayerScrollableArea::visibleHeight() const {
   return layer()->size().height();
 }
 
 int PaintLayerScrollableArea::visibleWidth() const {
   return layer()->size().width();
 }
 
 IntSize PaintLayerScrollableArea::contentsSize() const {
   return IntSize(pixelSnappedScrollWidth(), pixelSnappedScrollHeight());
@@ skipping 11 matching lines @@
 }
 
 bool PaintLayerScrollableArea::shouldSuspendScrollAnimations() const {
   LayoutView* view = box().view();
   if (!view)
     return true;
   return view->frameView()->shouldSuspendScrollAnimations();
 }
 
 void PaintLayerScrollableArea::scrollbarVisibilityChanged() {
+  updateScrollbarsEnabledState();
   if (LayoutView* view = box().view())
     return view->clearHitTestCache();
 }
 
 bool PaintLayerScrollableArea::scrollbarsCanBeActive() const {
   LayoutView* view = box().view();
   if (!view)
     return false;
   return view->frameView()->scrollbarsCanBeActive();
 }
@@ skipping 76 matching lines @@
   if (overflowRect().isEmpty())
     return;
   LayoutPoint scrollableOverflow =
       m_overflowRect.location() -
       LayoutSize(box().borderLeft(), box().borderTop());
   setScrollOrigin(flooredIntPoint(-scrollableOverflow) +
                   box().originAdjustmentForScrollbars());
 }
 
 void PaintLayerScrollableArea::updateScrollDimensions() {
+  if (m_overflowRect.size() != box().layoutOverflowRect().size())
+    contentsResized();
   m_overflowRect = box().layoutOverflowRect();
   box().flipForWritingMode(m_overflowRect);
   updateScrollOrigin();
 }
 
 void PaintLayerScrollableArea::setScrollOffsetUnconditionally(
     const ScrollOffset& offset,
     ScrollType scrollType) {
   cancelScrollAnimation();
   scrollOffsetChanged(offset, scrollType);
 }
 
-void PaintLayerScrollableArea::didChangeScrollbarsHidden() {
-  updateScrollbarsEnabledState();
-}
-
 void PaintLayerScrollableArea::updateScrollbarsEnabledState() {
   // overflow:scroll should just enable/disable.
   if (box().style()->overflowX() == OverflowScroll && horizontalScrollbar()) {
     horizontalScrollbar()->setEnabled(hasHorizontalOverflow() &&
                                       !scrollbarsHidden());
   }
   if (box().style()->overflowY() == OverflowScroll && verticalScrollbar()) {
     verticalScrollbar()->setEnabled(hasVerticalOverflow() &&
                                     !scrollbarsHidden());
   }
@@ skipping 1292 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     clampScrollableAreas() {
   for (auto& scrollableArea : *s_needsClamp)
     scrollableArea->clampScrollOffsetsAfterLayout();
   delete s_needsClamp;
   s_needsClamp = nullptr;
 }
 
 }  // namespace blink