FrameView shouldn't apply scroll anchoring when root layer scrolling is enabled

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 810 matching lines @@
         m_viewportScrollableArea = RootFrameViewport::create(visualViewport, *layoutViewport);
     }
 
     if (!m_scrollAnchor.hasScroller())
         m_scrollAnchor.setScroller(m_viewportScrollableArea ? m_viewportScrollableArea : this);
 
     if (shouldPerformScrollAnchoring())
         m_scrollAnchor.save();
 }
 
+bool FrameView::shouldPerformScrollAnchoring() const
+{
+    return RuntimeEnabledFeatures::scrollAnchoringEnabled()
+        && m_frame->settings() && !m_frame->settings()->rootLayerScrolls()
+        && m_scrollAnchor.hasScroller()
+        && layoutBox()->style()->overflowAnchor() != AnchorNone;
+}
+
 static inline void layoutFromRootObject(LayoutObject& root)
 {
     LayoutState layoutState(root);
     root.layout();
 }
 
 void FrameView::prepareLayoutAnalyzer()
 {
     bool isTracing = false;
     TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("blink.debug.layout"), &isTracing);
@@ skipping 2807 matching lines @@
 
     adjustScrollPositionFromUpdateScrollbars();
 }
 
 void FrameView::adjustScrollPositionFromUpdateScrollbars()
 {
     DoublePoint clamped = clampScrollPosition(scrollPositionDouble());
     // Restore before clamping because clamping clears the scroll anchor.
     // TODO(ymalik): This same logic exists in PaintLayerScrollableArea.
     // Remove when root-layer-scrolls is enabled.
-    if (clamped != scrollPositionDouble() && shouldPerformScrollAnchoring() && m_scrollAnchor.hasScroller()) {
+    if (clamped != scrollPositionDouble() && shouldPerformScrollAnchoring()) {
         m_scrollAnchor.restore();
         clamped = clampScrollPosition(scrollPositionDouble());
     }
     if (clamped != scrollPositionDouble() || scrollOriginChanged()) {
         ScrollableArea::setScrollPosition(clamped, ProgrammaticScroll);
         resetScrollOriginChanged();
     }
 }
 
 IntRect FrameView::rectToCopyOnScroll() const
@@ skipping 617 matching lines @@
 }
 
 bool FrameView::canThrottleRendering() const
 {
     if (!RuntimeEnabledFeatures::renderingPipelineThrottlingEnabled())
         return false;
     return m_subtreeThrottled || (m_hiddenForThrottling && m_crossOriginForThrottling);
 }
 
 } // namespace blink