Skip PaintPhaseDescendantOutlinesOnly if no descendent outlines in the layer

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

Index: third_party/WebKit/Source/core/layout/LayoutObject.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.cpp b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
index 9da07a0210cec65d327a9a99ef09cf9b1a8e2c6b..cc54da82c6af4e60832a94f13bf8c60a24e1fe44 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
@@ -1385,6 +1385,12 @@ inline void LayoutObject::invalidateSelectionIfNeeded(const LayoutBoxModelObject
 
 PaintInvalidationReason LayoutObject::invalidatePaintIfNeeded(PaintInvalidationState& paintInvalidationState, const LayoutBoxModelObject& paintInvalidationContainer)
 {
+    if (styleRef().hasOutline()) {
+        PaintLayer* layer = enclosingLayer()->enclosingSelfPaintingLayer();

[chrishtr, 2016/01/12 23:52:24]

This is a tree walk for every LayoutObject. PaintInvalidationState goes to great
lengths to avoid this for paint invalidation container, I don't think we can
afford this cost...

[Xianzhu, 2016/01/13 00:11:03]

Not every LayoutObject, but only LayoutObject having outline which is relatively
rare.

Just noticed that we already have such tree walk in
LayoutObject::invalidateDisplayItemClients(), but there haven't been performance
regressions reported, so we should definitely fix this. Will land the fix before
this CL.

[chrishtr, 2016/01/13 05:01:17]

I'll wait for that patch first then.

+        if (layer->layoutObject() != this)

[chrishtr, 2016/01/12 23:52:24]

Why this conditional?

[Xianzhu, 2016/01/13 00:11:03]

We paint self outline and child outlines in different phases. Here we need to
exclude self outline.

+            layer->setNeedsPaintPhaseChildOutlines();
+    }
+
     LayoutView* v = view();
     if (v->document().printing())
         return PaintInvalidationNone; // Don't invalidate paints if we're printing.