Update PaintLayer::needsPaintPhaseXXX flags when add/remove layer on style change

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 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 277 matching lines @@
             if (newStyleIsViewportConstained && layer())
                 frameView->addViewportConstrainedObject(this);
             else
                 frameView->removeViewportConstrainedObject(this);
         }
     }
 }
 
 void LayoutBoxModelObject::createLayer(PaintLayerType type)
 {
-    // If the current paint invalidation container is not a stacking context and this object is
-    // stacked content, creating this layer may cause this object and its
-    // descendants to change paint invalidation container. Therefore we must eagerly invalidate
-    // them on the original paint invalidation container before creating the layer.
-    if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled() && isRooted() && styleRef().isStacked()) {
-        const LayoutBoxModelObject& currentPaintInvalidationContainer = containerForPaintInvalidation();
-        if (!currentPaintInvalidationContainer.styleRef().isStackingContext())
-            invalidatePaintIncludingNonSelfPaintingLayerDescendants(currentPaintInvalidationContainer);
-    }
-

[Xianzhu, 2016/04/08 18:08:48]

This is moved into PaintLayer::insertOnlyThisLayer() to make the logic symmetric
with PaintLayer::removeOnlyThisLayer(). This method is the only caller of
PaintLayer::insertOnlyThisLayer().

[pdr., 2016/04/08 19:46:07]

Is this safe to move? The comment says that we must do this invalidation before
m_layer is changed because the containerForPaintInvalidation may change.

If it's necessary, we could preserve the original logic by passing the original
containerForPaintInvalidation to insertOnlyThisLayer.

[Xianzhu, 2016/04/08 21:30:55]

You're right. Thanks for scheduling the dry-run. It does break layout tests.

Modified containerForPaintInvalidation() to
parent()->containerForPaintInvalidation() in PaintLayer::insertOnlyThisLayer()
to get the original paint invalidation container before creating the layer.

     ASSERT(!m_layer);
     m_layer = adoptPtr(new PaintLayer(this, type));
     setHasLayer(true);
     m_layer->insertOnlyThisLayer();
 }
 
 void LayoutBoxModelObject::destroyLayer()
 {
     setHasLayer(false);
     m_layer = nullptr;
@@ skipping 651 matching lines @@
     if (rootElementStyle->hasBackground())
         return false;
 
     if (node() != document().firstBodyElement())
         return false;
 
     return true;
 }
 
 } // namespace blink