Replace the DownloadFileManager with direct ownership

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/bind.h"
 #include "base/file_util.h"
 #include "base/format_macros.h"
 #include "base/logging.h"
@@ skipping 202 matching lines @@
                    const net::BoundNetLog& bound_net_log)
     : full_path_(full_path),
       source_url_(source_url),
       referrer_url_(referrer_url),
       file_stream_(file_stream),
       bytes_so_far_(received_bytes),
       start_tick_(base::TimeTicks::Now()),
       calculate_hash_(calculate_hash),
       detached_(false),
       bound_net_log_(bound_net_log) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   memcpy(sha256_hash_, kEmptySha256Hash, kSha256HashLen);
   if (file_stream_.get()) {
     file_stream_->SetBoundNetLogSource(bound_net_log_);
     file_stream_->EnableErrorStatistics();
   }
 
   if (calculate_hash_) {
     secure_hash_.reset(crypto::SecureHash::Create(crypto::SecureHash::SHA256));
     if ((bytes_so_far_ > 0) &&  // Not starting at the beginning.
         (hash_state != "") &&  // Reasonably sure we have a hash state.
@@ skipping 317 matching lines @@
   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());
 }