Merge 159454 - Flush at the end of local file writing in FileWriter API.

net/base/file_stream.h

 // Copyright (c) 2012 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 179 matching lines @@
   // position is returned, or a value < 0 on error.
   // WARNING: one may not truncate a file beyond its current length on any
   //   platform with this call.
   virtual int64 Truncate(int64 bytes);
 
   // 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.
+  // The file must be opened with PLATFORM_FILE_ASYNC, and a non-null
+  // callback must be passed to this method. If the write could not
+  // complete synchronously, then ERR_IO_PENDING is returned, and the
+  // callback will be run on the thread where Flush() was called when
+  // the write has completed.
+  //
+  // It is valid to destroy or close the file stream while there is an
+  // asynchronous flush in progress.  That will cancel the flush and allow
+  // the buffer to be freed.
+  //
+  // It is invalid to request any asynchronous operations while there is an
+  // in-flight asynchronous operation.
   //
   // This method should not be called if the stream was opened READ_ONLY.
-  virtual int Flush();
+  virtual int Flush(const CompletionCallback& callback);
+
+  // 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.
+  virtual int FlushSync();
 
   // Turns on UMA error statistics gathering.
   void EnableErrorStatistics();
 
   // Sets the source reference for net-internals logging.
   // Creates source dependency events between |owner_bound_net_log| and
   // |bound_net_log_|.  Each gets an event showing the dependency on the other.
   // If only one of those is valid, it gets an event showing that a change
   // of ownership happened, but without details.
   void SetBoundNetLogSource(const net::BoundNetLog& owner_bound_net_log);
 
   // Returns the underlying platform file for testing.
   base::PlatformFile GetPlatformFileForTesting();
 
  private:
 #if defined(OS_WIN)
   FileStreamWin impl_;
 #elif defined(OS_POSIX)
   FileStreamPosix impl_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(FileStream);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_FILE_STREAM_H_