Update layer position on scroll origin change

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 721 matching lines @@
   if (layout_view_item.IsNull())
     return;
 
   ASSERT(frame_->View() == this);
 
   const IntRect rect = layout_view_item.DocumentRect();
   const IntSize& size = rect.size();
 
   const IntPoint origin(-rect.X(), -rect.Y());
   if (ScrollOrigin() != origin) {
-    ScrollableArea::SetScrollOrigin(origin);
+    SetScrollOrigin(origin);
     // setContentSize (below) also calls updateScrollbars so we can avoid
     // updating scrollbars twice by skipping the call here when the content
     // size does not change.
     if (!frame_->GetDocument()->Printing() && size == ContentsSize())
       UpdateScrollbars();
   }
 
   SetContentsSize(size);
 }
 
@@ skipping 3587 matching lines @@
     FrameRectsChanged();
     PositionScrollbarLayers();
     UpdateScrollCorner();
   }
 
   AdjustScrollOffsetFromUpdateScrollbars();
 }
 
 void FrameView::AdjustScrollOffsetFromUpdateScrollbars() {
   ScrollOffset clamped = ClampScrollOffset(GetScrollOffset());
-  if (clamped != GetScrollOffset() || ScrollOriginChanged()) {
-    ScrollableArea::SetScrollOffset(clamped, kClampingScroll);
-    ResetScrollOriginChanged();
-  }
+  if (clamped != GetScrollOffset() || ScrollOriginChanged())
+    SetScrollOffset(clamped, kClampingScroll);
 }
 
 void FrameView::ScrollContentsIfNeeded() {
   if (pending_scroll_delta_.IsZero())
     return;
   ScrollOffset scroll_delta = pending_scroll_delta_;
   pending_scroll_delta_ = ScrollOffset();
   // FIXME: Change scrollContents() to take DoubleSize. crbug.com/414283.
   ScrollContents(FlooredIntSize(scroll_delta));
 }
@@ skipping 162 matching lines @@
     graphics_layer->SetNeedsDisplay();
   graphics_layer->SetSize(FloatSize(corner_rect.size()));
 }
 
 void FrameView::PositionScrollbarLayers() {
   PositionScrollbarLayer(LayerForHorizontalScrollbar(), HorizontalScrollbar());
   PositionScrollbarLayer(LayerForVerticalScrollbar(), VerticalScrollbar());
   PositionScrollCornerLayer(LayerForScrollCorner(), ScrollCornerRect());
 }
 
+bool FrameView::UpdateAfterCompositingChange() {
+  if (ScrollOriginChanged()) {
+    // If the scroll origin changed, we need to update the layer position on
+    // the compositor since the offset itself might not have changed.
+    LayoutViewItem layout_view_item = this->GetLayoutViewItem();
+    if (!layout_view_item.IsNull() && layout_view_item.UsesCompositing())
+      layout_view_item.Compositor()->FrameViewDidScroll();
+    ResetScrollOriginChanged();
+  }
+  return false;
+}
+
 bool FrameView::UserInputScrollable(ScrollbarOrientation orientation) const {
   Document* document = GetFrame().GetDocument();
   Element* fullscreen_element = Fullscreen::FullscreenElementFrom(*document);
   if (fullscreen_element && fullscreen_element != document->documentElement())
     return false;
 
   if (RuntimeEnabledFeatures::rootLayerScrollingEnabled())
     return false;
 
   ScrollbarMode mode = (orientation == kHorizontalScrollbar)
@@ skipping 791 matching lines @@
 void FrameView::SetAnimationHost(
     std::unique_ptr<CompositorAnimationHost> host) {
   animation_host_ = std::move(host);
 }
 
 LayoutUnit FrameView::CaretWidth() const {
   return LayoutUnit(GetHostWindow()->WindowToViewportScalar(1));
 }
 
 }  // namespace blink