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

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

Index: third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp b/third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp
index 067a7670c8ff7bdc58a885aa755c4b874132039e..41b8b99b7f5c6b5c5bafcf4c5d802b92d5f745ae 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp
@@ -295,16 +295,6 @@ void LayoutBoxModelObject::styleDidChange(StyleDifference diff, const ComputedSt
 
 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);