Record UMA statistics for file_stream operations.

net/base/file_stream.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines FileStream, a basic interface for reading and writing files
 // synchronously or asynchronously with support for seeking to an offset.
 // Note that even when used asynchronously, only one operation is supported at
 // a time.
 
 #ifndef NET_BASE_FILE_STREAM_H_
@@ skipping 114 matching lines @@
   // Forces out a filesystem sync on this file to make sure that the file was
   // written out to disk and is not currently sitting in the buffer. This does
   // not have to be called, it just forces one to happen at the time of
   // calling.
   //
   /// Returns an error code if the operation could not be performed.
   //
   // This method should not be called if the stream was opened READ_ONLY.
   int Flush();
 
+  // Turns on UMA error statistics gathering.
+  void EnableErrorStatistics();
+
  private:
   class AsyncContext;
   friend class AsyncContext;
 
   // This member is used to support asynchronous reads.  It is non-null when
   // the FileStream was opened with PLATFORM_FILE_ASYNC.
   scoped_ptr<AsyncContext> async_context_;
 
   base::PlatformFile file_;
   int open_flags_;
   bool auto_closed_;
+  bool record_uma_;
 
   DISALLOW_COPY_AND_ASSIGN(FileStream);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_FILE_STREAM_H_