Revert of Avoid cross thread malloc / free pair of IOBuffer on the simple cache

net/disk_cache/simple/simple_entry_impl.h

Index: net/disk_cache/simple/simple_entry_impl.h
diff --git a/net/disk_cache/simple/simple_entry_impl.h b/net/disk_cache/simple/simple_entry_impl.h
index 6adf6007d000013b4bc3a9e5c7d450672121737a..5b58b555c29804f0340823981155f0fda9210b3f 100644
--- a/net/disk_cache/simple/simple_entry_impl.h
+++ b/net/disk_cache/simple/simple_entry_impl.h
@@ -253,14 +253,10 @@
                              std::unique_ptr<int> result);
 
   // Called after an asynchronous write completes.
-  // |buf| parameter brings back a reference to net::IOBuffer to the original
-  // thread, so that we can reduce cross thread malloc/free pair.
-  // See http://crbug.com/708644 for details.
   void WriteOperationComplete(int stream_index,
                               const CompletionCallback& completion_callback,
                               std::unique_ptr<SimpleEntryStat> entry_stat,
-                              std::unique_ptr<int> result,
-                              net::IOBuffer* buf);
+                              std::unique_ptr<int> result);
 
   void ReadSparseOperationComplete(
       const CompletionCallback& completion_callback,