Viewport resize anchoring should use the current layout viewport.

third_party/WebKit/Source/core/frame/RootFrameViewport.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef RootFrameViewport_h
 #define RootFrameViewport_h
 
 #include "core/CoreExport.h"
 #include "platform/scroll/ScrollableArea.h"
 
@@ skipping 15 matching lines @@
 public:
     static RootFrameViewport* create(ScrollableArea& visualViewport, ScrollableArea& layoutViewport)
     {
         return new RootFrameViewport(visualViewport, layoutViewport);
     }
 
     DECLARE_VIRTUAL_TRACE();
 
     void setLayoutViewport(ScrollableArea&);
 
+    void restoreToAnchor(const DoublePoint&);
+
     // ScrollableArea Implementation
     bool isRootFrameViewport() const override { return true; }
     void setScrollPosition(const DoublePoint&, ScrollType, ScrollBehavior = ScrollBehaviorInstant) override;
     LayoutRect scrollIntoView(
         const LayoutRect& rectInContent,
         const ScrollAlignment& alignX,
         const ScrollAlignment& alignY,
         ScrollType = ProgrammaticScroll) override;
     DoubleRect visibleContentRectDouble(IncludeScrollbarsInRect = ExcludeScrollbars) const override;
     IntRect visibleContentRect(IncludeScrollbarsInRect = ExcludeScrollbars) const override;
@@ skipping 52 matching lines @@
 
     Member<ScrollableArea> m_visualViewport;
     Member<ScrollableArea> m_layoutViewport;
 };
 
 DEFINE_TYPE_CASTS(RootFrameViewport, ScrollableArea, scrollableArea, scrollableArea->isRootFrameViewport(), scrollableArea.isRootFrameViewport());
 
 } // namespace blink
 
 #endif // RootFrameViewport_h