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

third_party/WebKit/Source/core/fetch/ImageResource.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@kde.org>
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007 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 142 matching lines @@
   void onePartInMultipartReceived(const ResourceResponse&) final;
   void multipartDataReceived(const char*, size_t) final;
 
   // Used by tests.
   bool isPlaceholder() const { return m_isPlaceholder; }
 
   bool shouldReloadBrokenPlaceholder() const {
     return m_isPlaceholder && willPaintBrokenImage();
   }
 
+  void setNotRefetchableDataFromDiskCache() {
+    m_isRefetchableDataFromDiskCache = false;
+  }
+
   DECLARE_VIRTUAL_TRACE();
 
  private:
   explicit ImageResource(blink::Image*, const ResourceLoaderOptions&);
 
   enum class MultipartParsingState : uint8_t {
     WaitingForFirstPart,
     ParsingFirstPart,
     FinishedParsingFirstPart,
   };
@@ skipping 44 matching lines @@
   // because reloadIfLoFi() was called.
   bool m_isSchedulingReload;
 
   // Indicates if this ImageResource is either attempting to load a placeholder
   // image, or is a (possibly broken) placeholder image.
   bool m_isPlaceholder;
 
   Timer<ImageResource> m_flushTimer;
   double m_lastFlushTime = 0.;
   Image::SizeAvailability m_sizeAvailable = Image::SizeUnavailable;
+
+  // Indicates if this resource's encoded image data can be purged and refetched
+  // from disk cache to save memory usage. See crbug/664437.
+  bool m_isRefetchableDataFromDiskCache;
 };
 
 DEFINE_RESOURCE_TYPE_CASTS(Image);
 
 }  // namespace blink
 
 #endif