Save previous paint offset in LayoutObject

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 221 matching lines @@
     , m_node(node)
     , m_parent(nullptr)
     , m_previous(nullptr)
     , m_next(nullptr)
 #if ENABLE(ASSERT)
     , m_hasAXObject(false)
     , m_setNeedsLayoutForbidden(false)
 #endif
     , m_bitfields(node)
 {
+    // TODO(wangxianzhu): Move this into initialization list when we enable the feature by default.
+    if (RuntimeEnabledFeatures::slimmingPaintOffsetCachingEnabled())
+        m_previousPositionFromPaintInvalidationBacking = uninitializedPaintOffset();
+
 #ifndef NDEBUG
     layoutObjectCounter.increment();
 #endif
     InstanceCounters::incrementCounter(InstanceCounters::LayoutObjectCounter);
 }
 
 LayoutObject::~LayoutObject()
 {
     ASSERT(!m_hasAXObject);
 #ifndef NDEBUG
@@ skipping 3139 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         fprintf(stderr, "Cannot showLayoutTree. Root is (nil)\n");
     }
 }
 
 #endif