Tweak priorities of paint invalidation reasons

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

Index: third_party/WebKit/Source/core/layout/LayoutObject.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.h b/third_party/WebKit/Source/core/layout/LayoutObject.h
index 1d8e50943ea4e6769357826b1a6a10892cd9dc1e..a724a4914c60075d5e8cf17fdd12fc570187276b 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.h
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.h
@@ -1123,11 +1123,11 @@ public:
     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.