[tracing] Support BACKGROUND mode in MemoryCache dump provider

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 92 matching lines @@
     ResourcePriority priorityFromObservers() override;
 
     void allClientsAndObserversRemoved() override;
 
     PassRefPtr<SharedBuffer> resourceBuffer() const override;
     void appendData(const char*, size_t) override;
     void error(const ResourceError&) override;
     void responseReceived(const ResourceResponse&, std::unique_ptr<WebDataConsumerHandle>) override;
     void finish(double finishTime = 0.0) override;
 
+    void onMemoryDump(WebMemoryDumpLevelOfDetail, WebProcessMemoryDump*) const override;
+
     // For compatibility, images keep loading even if there are HTTP errors.
     bool shouldIgnoreHTTPStatusCodeErrors() const override { return true; }
 
     bool isImage() const override { return true; }
 
     // ImageObserver
     void decodedSizeChangedTo(const blink::Image*, size_t newSize) override;
     void didDraw(const blink::Image*) override;
 
     bool shouldPauseAnimation(const blink::Image*) override;
@@ skipping 56 matching lines @@
     bool m_hasDevicePixelRatioHeaderValue;
     HashCountedSet<ImageResourceObserver*> m_observers;
     HashCountedSet<ImageResourceObserver*> m_finishedObservers;
 };
 
 DEFINE_RESOURCE_TYPE_CASTS(Image);
 
 } // namespace blink
 
 #endif