Early-out from the prepaint tree walk

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 2049367d76af354817202b78d02a37dc94f97772..2e5d49956ccb987cb43e61b87bfcba2847fb71d8 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
@@ -2734,8 +2734,17 @@ void LayoutObject::willBeRemovedFromTree() {
 
 void LayoutObject::setNeedsPaintPropertyUpdate() {
   m_bitfields.setNeedsPaintPropertyUpdate(true);
+  // |paintInvalidationParent()| is used to ensure we continue marking across

[chrishtr, 2016/12/01 02:36:34]

I don't think this comment is necessary.

+  // frame boundaries.
+  if (LayoutObject* ancestor = paintInvalidationParent())
+    ancestor->setDescendantNeedsPaintPropertyUpdate();
+}
+
+void LayoutObject::setDescendantNeedsPaintPropertyUpdate() {

[chrishtr, 2016/12/01 02:36:35]

*markAncestorChain* is how other bit-setting methods are named for other tree
walks, like layout and
descendant-dependent PaintLayer flags.

+  if (m_bitfields.descendantNeedsPaintPropertyUpdate())
+    return;
+  m_bitfields.setDescendantNeedsPaintPropertyUpdate(true);
 
-  // Mark all ancestors as having a descendant needing paint property updates.
   // |paintInvalidationParent()| is used to ensure we continue marking across
   // frame boundaries.
   LayoutObject* ancestor = paintInvalidationParent();