Move computation of 3D descendants to the descendant-dependent flags walk.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintPropertyTreeBuilder.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutInline.h"
@@ skipping 289 matching lines @@
 
   if (object.paintProperties() && object.paintProperties()->transform()) {
     context.current.transform = object.paintProperties()->transform();
     context.current.shouldFlattenInheritedTransform = false;
     context.current.renderingContextID = 0;
   }
 }
 
 static CompositingReasons compositingReasonsForTransform(
     const LayoutObject& object) {
+  const ComputedStyle& style = object.styleRef();
   CompositingReasons compositingReasons = CompositingReasonNone;
   if (CompositingReasonFinder::requiresCompositingForTransform(object))
     compositingReasons |= CompositingReason3DTransform;
 
-  if (CompositingReasonFinder::requiresCompositingForTransformAnimation(
-          object.styleRef()))
+  if (CompositingReasonFinder::requiresCompositingForTransformAnimation(style))
     compositingReasons |= CompositingReasonActiveAnimation;
 
-  if (object.styleRef().hasWillChangeCompositingHint() &&
-      !object.styleRef().subtreeWillChangeContents())
+  if (style.hasWillChangeCompositingHint() &&
+      !style.subtreeWillChangeContents())
     compositingReasons |= CompositingReasonWillChangeCompositingHint;
 
-  if (object.isBoxModelObject()) {
+  if (object.isBoxModelObject() &&

[Xianzhu, 2016/12/28 18:08:11]

Not related to the change, but just a question: we support non-box object here,
but don't  in updateTransform() (which doesn't create transform node if
!object.isBox()). Is there any problem?

+      (style.hasPerspective() ||
+       style.usedTransformStyle3D() == TransformStyle3DPreserve3D)) {
     const LayoutBoxModelObject* box = toLayoutBoxModelObject(&object);
     if (box->hasLayer()) {
-      // TODO(chrishtr): move this to the descendant-dependent flags recursion
-      // PaintLayer::updateDescendantDependentFlags.
-      box->layer()->update3DTransformedDescendantStatus();
-
       if (box->layer()->has3DTransformedDescendant())
         compositingReasons |= CompositingReason3DTransform;
     }
   }
 
   return compositingReasons;
 }
 
 static FloatPoint3D transformOrigin(const LayoutBox& box) {
   const ComputedStyle& style = box.styleRef();
@@ skipping 649 matching lines @@
   updateOverflowClip(object, context);
   updatePerspective(object, context);
   updateSvgLocalToBorderBoxTransform(object, context);
   updateScrollAndScrollTranslation(object, context);
   updateOutOfFlowContext(object, context);
 
   context.forceSubtreeUpdate |= object.subtreeNeedsPaintPropertyUpdate();
 }
 
 }  // namespace blink