Update paint property subtrees on paint offset changes

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 903 matching lines @@
     // This is a weird quirk that table cells paint as children of table rows,
     // but their location have the row's location baked-in.
     // Similar adjustment is done in LayoutTableCell::offsetFromContainer().
     if (boxModelObject.isTableCell()) {
       LayoutObject* parentRow = boxModelObject.parent();
       DCHECK(parentRow && parentRow->isTableRow());
       context.current.paintOffset.moveBy(
           -toLayoutBox(parentRow)->physicalLocation());
     }
   }
+
+  // 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)
+    context.forceSubtreeUpdate = true;

[pdr., 2016/12/16 03:24:09]

This is the main change in this patch. Instead of using
object.setNeedsPaintPropertyUpdate(), we force the entire subtree to be updated.

 }
 
 void PaintPropertyTreeBuilder::updatePropertiesForSelf(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   if (!object.isBoxModelObject() && !object.isSVG())
     return;
 
 #if DCHECK_IS_ON()
   FindObjectPropertiesNeedingUpdateScope checkNeedsUpdateScope(object, context);
@@ skipping 18 matching lines @@
 #endif
 
   updateOverflowClip(object, context);
   updatePerspective(object, context);
   updateSvgLocalToBorderBoxTransform(object, context);
   updateScrollAndScrollTranslation(object, context);
   updateOutOfFlowContext(object, context);
 }
 
 }  // namespace blink