Add new UMA stats for parallelizable download

content/browser/download/download_file.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.
 
 #ifndef CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 29 matching lines @@
   // error.
   typedef base::Callback<void(DownloadInterruptReason reason,
                               const base::FilePath& path)>
       RenameCompletionCallback;
 
   virtual ~DownloadFile() {}
 
   // Upon completion, |callback| will be called on the UI
   // thread as per the comment above, passing DOWNLOAD_INTERRUPT_REASON_NONE
   // on success, or a network download interrupt reason on failure.
-  virtual void Initialize(
-      const InitializeCallback& callback,
-      const DownloadItem::ReceivedSlices& received_slices) = 0;
+  virtual void Initialize(const InitializeCallback& callback,

[xingliu, 2017/04/19 02:18:11]

FYI: sorry that I just modified this function, so you probably need to rebase.
It might cause some issue if we want to cherry pick this commit, we might need
to cherry pick another first.

[qinmin, 2017/04/19 22:42:33]

rebased in the new PS

+                          const DownloadItem::ReceivedSlices& received_slices,
+                          bool is_parallelizable) = 0;
 
   // Add a byte stream reader to write into a slice of the file, used for
   // parallel download. Called on the file thread.
   virtual void AddByteStream(std::unique_ptr<ByteStreamReader> stream_reader,
                              int64_t offset,
                              int64_t length) = 0;
 
   // Rename the download file to |full_path|.  If that file exists
   // |full_path| will be uniquified by suffixing " (<number>)" to the
   // file name before the extension.
@@ skipping 24 matching lines @@
   virtual void SetPotentialFileLength(int64_t length) = 0;
 
   virtual const base::FilePath& FullPath() const = 0;
   virtual bool InProgress() const = 0;
   virtual void WasPaused() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_H_