Make FileStream::Seek async and add FileStream::SeekSync for sync operation

content/browser/download/base_file.cc

 // 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.
 
 #include "content/browser/download/base_file.h"
 
 #include "base/file_util.h"
 #include "base/format_macros.h"
 #include "base/logging.h"
 #include "base/pickle.h"
@@ skipping 492 matching lines @@
     CreateFileStream();
     file_stream_->EnableErrorStatistics();
     int open_result = file_stream_->OpenSync(
         full_path_,
         base::PLATFORM_FILE_OPEN_ALWAYS | base::PLATFORM_FILE_WRITE);
     if (open_result != net::OK)
       return ClearStream(LOG_ERROR("Open", open_result));
 
     // We may be re-opening the file after rename. Always make sure we're
     // writing at the end of the file.
-    int64 seek_result = file_stream_->Seek(net::FROM_END, 0);
+    int64 seek_result = file_stream_->SeekSync(net::FROM_END, 0);
     if (seek_result < 0)
       return ClearStream(LOG_ERROR("Seek", seek_result));
   } else {
     file_stream_->SetBoundNetLogSource(bound_net_log_);
   }
 
 #if defined(OS_WIN)
   AnnotateWithSourceInformation();
 #endif
 
@@ skipping 38 matching lines @@
 int64 BaseFile::CurrentSpeedAtTime(base::TimeTicks current_time) const {
   base::TimeDelta diff = current_time - start_tick_;
   int64 diff_ms = diff.InMilliseconds();
   return diff_ms == 0 ? 0 : bytes_so_far() * 1000 / diff_ms;
 }
 
 int64 BaseFile::CurrentSpeed() const {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   return CurrentSpeedAtTime(base::TimeTicks::Now());
 }