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

[Xianzhu, 2015/10/13 23:58:12]

Conditions are made stricter here to avoid duplicated invalidations and avoid
potential performance issues when creating large number of layers.

Paint invalidation container changes caused by compositing update are already
handled by CompositingLayerMapping. Here we handle paint invalidation container
change not covered by compositing update only.

+        }
     }
 
     ASSERT(!m_layer);