Add UMA for estimating disk bandwidth and the time saved with parallel download

content/browser/download/download_file.h

Index: content/browser/download/download_file.h
diff --git a/content/browser/download/download_file.h b/content/browser/download/download_file.h
index c155cb216ee8c8385b094ad9d0156afeb67c9119..06ff940d1beab5a717d0b9da9d9e1d8ac0a7b8f8 100644
--- a/content/browser/download/download_file.h
+++ b/content/browser/download/download_file.h
@@ -76,6 +76,7 @@ class CONTENT_EXPORT DownloadFile {
 
   virtual const base::FilePath& FullPath() const = 0;
   virtual bool InProgress() const = 0;
+  virtual void Pause() {}

[xingliu, 2017/03/17 00:02:15]

The methods here are all pure virtual, can we also make it pure virtual?
It only has two subclasses, so shouldn't be too much work.

nit%: Maybe add a comment here, since Pause call is not actually pause the
download, but mainly for metric purpose.

[David Trainor- moved to gerrit, 2017/03/17 07:25:40]

WasPaused?

[qinmin, 2017/03/17 19:52:54]

Done. Changed to WasPaused() as suggested by David

[qinmin, 2017/03/17 19:52:54]

Done.

 };
 
 }  // namespace content