Combine LayoutObject::previousPaintOffset and paintOffset in paint properties

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
index 57fc3e24b1c1741c00b35ba8b356c4463ae97d4e..d6d2ca50bb0a9ced20f53e2167789373e375f54a 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
@@ -569,6 +569,8 @@ void PaintPropertyTreeBuilder::updateLocalBorderBoxContext(
   if (!object.needsPaintPropertyUpdate() && !context.forceSubtreeUpdate)
     return;
 
+  object.getMutableForPainting().setPaintOffset(context.current.paintOffset);
+
   // Avoid adding an ObjectPaintProperties for non-boxes to save memory, since
   // we don't need them at the moment.
   if (!object.isBox() && !object.hasLayer()) {
@@ -577,8 +579,8 @@ void PaintPropertyTreeBuilder::updateLocalBorderBoxContext(
   } else {
     auto& properties = object.getMutableForPainting().ensurePaintProperties();
     properties.updateLocalBorderBoxProperties(
-        context.current.paintOffset, context.current.transform,
-        context.current.clip, context.currentEffect, context.current.scroll);
+        context.current.transform, context.current.clip, context.currentEffect,
+        context.current.scroll);
   }
 }
 
@@ -880,14 +882,14 @@ static void overrideContainingBlockContextFromRealContainingBlock(
       containingBlock.paintProperties()->localBorderBoxProperties();
   DCHECK(properties);
 
-  context.transform = properties->propertyTreeState.transform();
-  context.paintOffset = properties->paintOffset;
+  context.transform = properties->transform();
+  context.paintOffset = containingBlock.paintOffset();
   context.shouldFlattenInheritedTransform =
       context.transform && context.transform->flattensInheritedTransform();
   context.renderingContextId =
       context.transform ? context.transform->renderingContextId() : 0;
-  context.clip = properties->propertyTreeState.clip();
-  context.scroll = properties->propertyTreeState.scroll();
+  context.clip = properties->clip();
+  context.scroll = properties->scroll();
 }
 
 void PaintPropertyTreeBuilder::updateContextForBoxPosition(
@@ -973,15 +975,17 @@ void PaintPropertyTreeBuilder::updateContextForBoxPosition(
 
   // Many paint properties depend on paint offset so we force an update of
   // the entire subtree on paint offset changes.
-  if (object.previousPaintOffset() != context.current.paintOffset)
+  if (object.paintOffset() != context.current.paintOffset)
     context.forceSubtreeUpdate = true;
 }
 
 void PaintPropertyTreeBuilder::updatePropertiesForSelf(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
-  if (!object.isBoxModelObject() && !object.isSVG())
+  if (!object.isBoxModelObject() && !object.isSVG()) {
+    object.getMutableForPainting().setPaintOffset(context.current.paintOffset);

[pdr., 2017/01/06 18:27:42]

Do we need to check that an update is needed too? For example:
if (!object.isBoxModelObject() && !object.isSVG()) {
  if (object.needsPaintPropertyUpdate() || context.forceSubtreeUpdate)
    object.getMutableForPainting().setPaintOffset(context.current.paintOffset);
}

Also, I think the checkNeedsUpdateScope should be moved above this
setPaintOffset call.

WDYT about unifying both setPaintOffset calls in this function? Something like:
void PaintPropertyTreeBuilder::updatePropertiesForSelf(...) {
    checkNeedsUpdateScope...
    if (object.isBoxModelObject() || object.isSVG()) {
      do updates here...
    }
    object.getMutableForPainting().setPaintOffset(context.current.paintOffset);
}

[Xianzhu, 2017/01/06 19:24:18]

Done.
Done.
Done.

     return;
+  }
 
 #if DCHECK_IS_ON()
   FindObjectPropertiesNeedingUpdateScope checkNeedsUpdateScope(object, context);