Make disk_cache::TraceObject RefCountedThreadSafe instead of RefCounted

net/disk_cache/blockfile/trace.h

Index: net/disk_cache/blockfile/trace.h
diff --git a/net/disk_cache/blockfile/trace.h b/net/disk_cache/blockfile/trace.h
index 1c30dacb0fddb97844713682d97fff06ba17c62b..2cc2fa12ecf47d4ab81535f640b7c8620f6f24e0 100644
--- a/net/disk_cache/blockfile/trace.h
+++ b/net/disk_cache/blockfile/trace.h
@@ -21,8 +21,9 @@ void DestroyTrace(void);
 
 // Simple class to handle the trace buffer lifetime. Any object interested in
 // tracing should keep a reference to the object returned by GetTraceObject().
-class TraceObject : public base::RefCounted<TraceObject> {
-  friend class base::RefCounted<TraceObject>;
+class TraceObject : public base::RefCountedThreadSafe<TraceObject> {
+  friend class base::RefCountedThreadSafe<TraceObject>;
+
  public:
   static TraceObject* GetTraceObject();
   void EnableTracing(bool enable);