Subtree caching implementation in blink-core

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 59 matching lines @@
 class Page;
 class ScrollingCoordinator;
 class TracedValue;
 struct AnnotatedRegionValue;
 struct CompositedSelection;
 
 typedef unsigned long long DOMTimeStamp;
 
 class CORE_EXPORT FrameView final : public Widget, public ScrollableArea {
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(FrameView);
+
+    friend class DisplayItemListPaintTestForSlimmingPaintV2;
+    friend class Internals;
+    friend class LayoutPart; // for invalidateTreeIfNeeded
+    friend class LayoutView; // for contentRectangleForPaintInvalidation
+
 public:
-    friend class LayoutView;
-    friend class Internals;
-
     static PassRefPtrWillBeRawPtr<FrameView> create(LocalFrame*);
     static PassRefPtrWillBeRawPtr<FrameView> create(LocalFrame*, const IntSize& initialSize);
 
     ~FrameView() override;
 
     void invalidateRect(const IntRect&) override;
     void setFrameRect(const IntRect&) override;
 
     LocalFrame& frame() const
     {
@@ skipping 523 matching lines @@
     void compositeForSlimmingPaintV2();
 
     void reset();
     void init();
 
     void clearLayoutSubtreeRootsAndMarkContainingBlocks();
 
     // Called when our frame rect changes (or the rect/scroll position of an ancestor changes).
     void frameRectsChanged() override;
 
-    friend class LayoutPart;
-
     bool contentsInCompositedLayer() const;
 
     void applyOverflowToViewport(LayoutObject*, ScrollbarMode& hMode, ScrollbarMode& vMode);
 
     void updateCounters();
     void forceLayoutParentViewIfNeeded();
     void performPreLayoutTasks();
     void performLayout(bool inSubtreeLayout);
     void scheduleOrPerformPostLayoutTasks();
     void performPostLayoutTasks();
@@ skipping 222 matching lines @@
     static const unsigned visualPixelThreshold = 32 * 32;
     if (m_visuallyNonEmptyPixelCount > visualPixelThreshold)
         setIsVisuallyNonEmpty();
 }
 
 DEFINE_TYPE_CASTS(FrameView, Widget, widget, widget->isFrameView(), widget.isFrameView());
 
 } // namespace blink
 
 #endif // FrameView_h