Combine LayoutObject::previousPaintOffset and paintOffset in paint properties

third_party/WebKit/Source/core/paint/PrePaintTreeWalk.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/PrePaintTreeWalk.h"
 
 #include "core/dom/DocumentLifecycle.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/layout/LayoutMultiColumnSpannerPlaceholder.h"
@@ skipping 110 matching lines @@
     return descendantsFullyUpdated;
   }
 
   // This must happen before updateContextForBoxPosition, because the
   // latter reads some of the state computed uere.
   updateAuxiliaryObjectProperties(object, context);
 
   // Ensure the current context takes into account the box's position. This can
   // force a subtree update due to paint offset changes and must precede any
   // early out from the treewalk.
+  LayoutPoint oldPaintOffset = object.paintOffset();
   m_propertyTreeBuilder.updateContextForBoxPosition(object,
                                                     context.treeBuilderContext);
 
   // Early out from the treewalk if possible.
   if (!object.needsPaintPropertyUpdate() &&
       !object.descendantNeedsPaintPropertyUpdate() &&
       !context.treeBuilderContext.forceSubtreeUpdate &&
       !context.paintInvalidatorContext.forcedSubtreeInvalidationFlags &&
       !object
            .shouldCheckForPaintInvalidationRegardlessOfPaintInvalidationState()) {
     // Even though the subtree was not walked, we know that a walk will not
     // change anything and can return true as if the subtree was fully updated.
     return true;
   }
 
   m_propertyTreeBuilder.updatePropertiesForSelf(object,
                                                 context.treeBuilderContext);
-  m_paintInvalidator.invalidatePaintIfNeeded(object,
+  m_paintInvalidator.invalidatePaintIfNeeded(object, oldPaintOffset,
                                              context.paintInvalidatorContext);
   m_propertyTreeBuilder.updatePropertiesForChildren(object,
                                                     context.treeBuilderContext);
 
   bool descendantsFullyUpdated = true;
   for (const LayoutObject* child = object.slowFirstChild(); child;
        child = child->nextSibling()) {
     // Column spanners are walked through their placeholders. See above.
     if (child->isColumnSpanAll())
       continue;
@@ skipping 20 matching lines @@
 
   if (descendantsFullyUpdated) {
     // If descendants were not updated, do not clear flags. During the next
     // PrePaintTreeWalk, these flags will be used again.
     object.getMutableForPainting().clearPaintFlags();
   }
   return descendantsFullyUpdated;
 }
 
 }  // namespace blink