Oilpan: Remove most WillBe types from the code base

third_party/WebKit/Source/core/style/FillLayer.cpp

 /*
  * Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 11 matching lines @@
 #include "core/style/FillLayer.h"
 
 #include "core/layout/LayoutObject.h"
 #include "core/style/DataEquivalency.h"
 
 namespace blink {
 
 struct SameSizeAsFillLayer {
     FillLayer* m_next;
 
-    RefPtrWillBePersistent<StyleImage> m_image;
+    Persistent<StyleImage> m_image;
 
     Length m_xPosition;
     Length m_yPosition;
 
     LengthSize m_sizeLength;
 
     unsigned m_bitfields1;
     unsigned m_bitfields2;
 };
 
@@ skipping 376 matching lines @@
 {
     for (; layer1 && layer2; layer1 = layer1->next(), layer2 = layer2->next()) {
         if (!layerImagesIdentical(*layer1, *layer2))
             return false;
     }
 
     return !layer1 && !layer2;
 }
 
 } // namespace blink