Add UMA to estimate deroppable memory usage of encoded data size in Resources

third_party/WebKit/Source/core/style/StyleFetchedImage.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 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.
@@ skipping 50 matching lines @@
   void addClient(LayoutObject*) override;
   void removeClient(LayoutObject*) override;
   void notifyFinished(Resource*) override;
   String debugName() const override { return "StyleFetchedImage"; }
   PassRefPtr<Image> image(const LayoutObject&,
                           const IntSize&,
                           float zoom) const override;
   bool knownToBeOpaque(const LayoutObject&) const override;
   ImageResource* cachedImage() const override;
 
+  bool isRefetchableFromDiskCache() const override {
+    // ResourceFetcher is not determined from StyleFetchedImage and it is
+    // impossible to send a request for refetching.
+    return false;
+  }
+
   DECLARE_VIRTUAL_TRACE();
 
  private:
   StyleFetchedImage(ImageResource*, const Document&, const KURL&);
 
   void dispose();
 
   Member<ImageResource> m_image;
   Member<const Document> m_document;
   const KURL m_url;
 };
 
 DEFINE_STYLE_IMAGE_TYPE_CASTS(StyleFetchedImage, isImageResource());
 
 }  // namespace blink
 #endif