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 199 matching lines @@
   HashCountedSet<ImageResourceObserver*> m_observers;
   HashCountedSet<ImageResourceObserver*> m_finishedObservers;
 
   // Indicates if the ImageResource is currently scheduling a reload, e.g.
   // 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;
+
+  bool m_isRefetchableFromDiskCache;

[yhirano, 2016/11/16 11:25:38]

How about having a function that turns this flag off and calling the function
from the StylefetchedImage constructor?

[yhirano, 2016/11/16 11:25:38]

I think including "data" or "body" in the name is a good idea.
m_isAllowedToRefetchData[FromDiskCache], for example?

Anyway, please write some comments.

[hajimehoshi, 2016/11/16 12:15:48]

Done. (setNotRefetchableDataFromDiskCache seems weird. Do you have any
suggestion?)

[hajimehoshi, 2016/11/16 12:19:48]

I mean the name setNotRefetchableDataFromDiskCache is weird but I couldn't come
up with a better name...

[yhirano, 2016/11/17 02:16:56]

Is it better to focus on dropping / discarding the encoded data rather than
refeching in the field name? After all that is what you want to do. But it's up
to you.

 };
 
 DEFINE_RESOURCE_TYPE_CASTS(Image);
 
 }  // namespace blink
 
 #endif