wtf/CheckedArithmetic.h delegates to base/numerics/safe_math.h.

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

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@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
@@ skipping 363 matching lines @@
         }
 
     }
 }
 
 void ImageResource::decodedSizeChanged(const blink::Image* image, int delta)
 {
     if (!image || image != m_image)
         return;
 
-    // TODO(bsep): Crash on underflow, which is possible if an error causes
-    // decodedSize to be 0.
-    setDecodedSize(decodedSize() + delta);
+    WTF::CheckedNumeric<size_t> checkedDecodedSize(decodedSize());
+    checkedDecodedSize += delta;
+    setDecodedSize(checkedDecodedSize.ValueOrDie());
 }
 
 void ImageResource::didDraw(const blink::Image* image)
 {
     if (!image || image != m_image)
         return;
     // decodedSize() == 0 indicates that the image is decoded into DiscardableMemory,
     // not in MemoryCache. So we don't need to call Resource::didAccessDecodedData()
     // to update MemoryCache.
     if (decodedSize() != 0)
@@ skipping 94 matching lines @@
     if (response().wasFetchedViaServiceWorker())
         return response().serviceWorkerResponseType() != WebServiceWorkerResponseTypeOpaque;
     if (!getImage()->currentFrameHasSingleSecurityOrigin())
         return false;
     if (passesAccessControlCheck(securityOrigin))
         return true;
     return !securityOrigin->taintsCanvas(response().url());
 }
 
 } // namespace blink