Tweak priorities of paint invalidation reasons

third_party/WebKit/Source/core/layout/LayoutObject.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google 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 1105 matching lines @@
     // Invalidate the paint of a specific subrectangle within a given object. The rect is in the object's coordinate space.
     void invalidatePaintRectangle(const LayoutRect&) const;
 
     // Walk the tree after layout issuing paint invalidations for layoutObjects that have changed or moved, updating bounds that have changed, and clearing paint invalidation state.
     virtual void invalidateTreeIfNeeded(const PaintInvalidationState&);
 
     void invalidatePaintIncludingNonCompositingDescendants();
     void invalidatePaintIncludingNonSelfPaintingLayerDescendants(const LayoutBoxModelObject& paintInvalidationContainer);
     void setShouldDoFullPaintInvalidationIncludingNonCompositingDescendants();
 
-    // Returns true if the object will not generate any effective painted output.
+    // Returns true if the object will not generate any effective painted output regardless of current size.

[pdr., 2016/08/15 23:37:42]

The text you wrote in your change description was useful for me to understand
this. Could you add it here?

Something like:
// Return true if the object will not generate any effective painted output no
matter what size the
// object is. For example, this function can return false for an object of size
0x0 because of
// visual overflowing effects or clips that affect children.

(is that last sentence true? If not, maybe just leave it at "For example, this
function can return false for an object of size 0x0.")

[Xianzhu, 2016/08/16 01:13:54]

Done (with a slightly different explanation).

     // It's used to skip unforced paint invalidation (which is when shouldDoFullPaintInvalidation
     // is false, but mayNeedPaintInvalidation or childShouldCheckForPaintInvalidation is true) to
     // avoid unnecessary paint invalidations of empty areas covered by such objects.
-    virtual bool paintedOutputOfObjectHasNoEffect() const { return false; }
+    virtual bool paintedOutputOfObjectHasNoEffectRegardlessOfSize() const { return false; }
 
     // Returns the rect that should have paint invalidated whenever this object changes. The rect is in the view's
     // coordinate space. This method deals with outlines and overflow.
     virtual LayoutRect absoluteClippedOverflowRect() const;
 
     // Returns the rect that should have paint invalidated whenever this object changes. The rect is in the object's
     // local coordinate space. This is for non-SVG objects and LayoutSVGRoot only. SVG objects (except LayoutSVGRoot)
     // should use paintInvalidationRectInLocalSVGCoordinates() and map with SVG transforms instead.
     virtual LayoutRect localOverflowRectForPaintInvalidation() const;
 
@@ skipping 1022 matching lines @@
 void showTree(const blink::LayoutObject*);
 void showLineTree(const blink::LayoutObject*);
 void showLayoutTree(const blink::LayoutObject* object1);
 // We don't make object2 an optional parameter so that showLayoutTree
 // can be called from gdb easily.
 void showLayoutTree(const blink::LayoutObject* object1, const blink::LayoutObject* object2);
 
 #endif
 
 #endif // LayoutObject_h