[SPInvaldation] Update subtree paint properties when a layout subtree is inserted

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

Index: third_party/WebKit/Source/core/layout/LayoutObjectChildList.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutObjectChildList.cpp b/third_party/WebKit/Source/core/layout/LayoutObjectChildList.cpp
index ecbe52c497b5027e7ccfbd818c25c4b6a7bee25b..d4ca0813cace9445ae0119c57c744043d83cee04 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObjectChildList.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObjectChildList.cpp
@@ -184,6 +184,7 @@ void LayoutObjectChildList::insertChildNode(LayoutObject* owner,
       LayoutInvalidationReason::AddedToLayout);
   newChild->setShouldDoFullPaintInvalidation(
       PaintInvalidationLayoutObjectInsertion);
+  newChild->setSubtreeNeedsPaintPropertyUpdate();

[pdr., 2016/12/16 02:17:28]

WDYT of making this more explicit by using a flag (or by putting the reason in
the function name instead of the update type)? I think this will help make it
clearer to folks outside the paint team which call is appropriate.

I'm thinking something like:
enum PaintPropertyUpdate {
  StyleOrLayoutChange
  InsertedIntoLayoutTree
}
newChild->setNeedsPaintPropertyUpdate(InsertedIntoLayoutTree);

We could then hide the details in LayoutObject::setNeedsPaintPropertyUpdate.

[Xianzhu, 2016/12/16 17:24:57]

I would still prefer subtree update flag because
- I'm planning to replace
FrameView::setShouldInvalidateAllPaintAndPaintProperties with this new flag
(https://codereview.chromium.org/2583733003/). Using the enum we would need
another value;
- The semantics of subtree update for callers in the two cases (insert child,
printing) seem all clear;
- I feel we might have other cases needing explicit subtree update semantics.

   if (!owner->normalChildNeedsLayout())
     owner->setChildNeedsLayout();  // We may supply the static position for an
                                    // absolute positioned child.