Invalidate the frame view when changing the background image of the document or body.

Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
@@ skipping 104 matching lines @@
     // Methods for getting/setting the size Blink should use to layout the contents.
     IntSize layoutSize(IncludeScrollbarsInRect = ExcludeScrollbars) const;
     void setLayoutSize(const IntSize&);
 
     // If this is set to false, the layout size will need to be explicitly set by the owner.
     // E.g. WebViewImpl sets its mainFrame's layout size manually
     void setLayoutSizeFixedToFrameSize(bool isFixed) { m_layoutSizeFixedToFrameSize = isFixed; }
     bool layoutSizeFixedToFrameSize() { return m_layoutSizeFixedToFrameSize; }
 
     bool needsFullPaintInvalidation() const { return m_doFullPaintInvalidation; }
+    void setNeedsFullPaintInvalidation() { m_doFullPaintInvalidation = true; }
 
     void updateAcceleratedCompositingSettings();
 
     void recalcOverflowAfterStyleChange();
 
     bool isEnclosedInCompositingLayer() const;
 
     void resetScrollbars();
     void prepareForDetach();
     void detachCustomScrollbars();
@@ skipping 692 matching lines @@
     }
 
 private:
     RawPtrWillBeMember<FrameView> m_view;
     bool m_originalValue;
 };
 
 } // namespace blink
 
 #endif // FrameView_h