[tracing] Support BACKGROUND mode in MemoryCache dump provider

third_party/WebKit/Source/platform/SharedBuffer.cpp

 /*
  * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 257 matching lines @@
     }
     return data;
 }
 
 void SharedBuffer::onMemoryDump(const String& dumpPrefix, WebProcessMemoryDump* memoryDump) const
 {
     if (m_buffer.size()) {
         WebMemoryAllocatorDump* dump = memoryDump->createMemoryAllocatorDump(dumpPrefix + "/shared_buffer");
         dump->addScalar("size", "bytes", m_buffer.size());
         memoryDump->addSuballocation(dump->guid(), String(WTF::Partitions::kAllocatedObjectPoolName));
-    } else {
+    }
+    if (m_segments.size()) {
         // If there is data in the segments, then it should have been allocated
         // using fastMalloc.
         const String dataDumpName = dumpPrefix + "/segments";
         auto dump = memoryDump->createMemoryAllocatorDump(dataDumpName);
-        dump->addScalar("size", "bytes", m_size);
+        dump->addScalar("size", "bytes", m_size - m_buffer.size());
         memoryDump->addSuballocation(dump->guid(), String(WTF::Partitions::kAllocatedObjectPoolName));
     }
 }
 
 } // namespace blink