Invalidate non-self-painting-layer descendants when creating a layer

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 1794f1c2bc07306de8fc59e3f16e6924de415167..dcf30ed39c937159c2dcbdb4bf999cbe9cc18526 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp
@@ -280,20 +280,15 @@ void LayoutBoxModelObject::styleDidChange(StyleDifference diff, const ComputedSt
 
 void LayoutBoxModelObject::createLayer(PaintLayerType type)
 {
-
-    // Acquiring a PaintLayer may change the paint invalidation container. Therefore we must eagerly
-    // invalidate paint for this object before creating the layer.
-    if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled() && isRooted()) {
-        DisablePaintInvalidationStateAsserts invalidationDisabler;
-        DisableCompositingQueryAsserts compositingDisabler;
-
-        // It would be more correct to call invalidatePaintIncludingNonCompositingDescendants, but
-        // we do this instead to avoid performance issues when creating large numbers of layers.
-        const LayoutBoxModelObject& paintInvalidationContainer = containerForPaintInvalidationOnRootedTree();
-        invalidatePaintUsingContainer(
-            paintInvalidationContainer,
-            boundsRectForPaintInvalidation(&paintInvalidationContainer),
-            PaintInvalidationLayer);
+    // If the current paint invalidation container is not a stacking context and this object is
+    // a or treated as a stacking context, 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().isTreatedAsOrStackingContext()) {

[chrishtr, 2015/10/14 17:43:00]

If an element gets a paint layer but isTreatedAsOrStackingContext is false,
can't it still change paint invalidation container and require eager
invalidation?

[Xianzhu, 2015/10/14 18:17:48]

If isTreatedAsOrStackingContext is false, its paint invalidation container is in
the chain of parent->stackingContextAncestor->..., which won't be affected by
creation of this layer.

+        if (const LayoutBoxModelObject* currentPaintInvalidationContainer = containerForPaintInvalidation()) {
+            if (!currentPaintInvalidationContainer->styleRef().isStackingContext())
+                invalidatePaintIncludingNonSelfPaintingLayerDescendants(*currentPaintInvalidationContainer);
+        }
     }
 
     ASSERT(!m_layer);