Avoid trying to delete a non-existent file.

content/browser/download/base_file.cc

Index: content/browser/download/base_file.cc
diff --git a/content/browser/download/base_file.cc b/content/browser/download/base_file.cc
index 405dc10e551935bb5852e63a496267abc386957a..ff0757017f793afe3b415851f00b15e5638797ce 100644
--- a/content/browser/download/base_file.cc
+++ b/content/browser/download/base_file.cc
@@ -182,6 +182,7 @@ void BaseFile::Cancel() {
   bound_net_log_.AddEvent(net::NetLog::TYPE_CANCELLED);
 
   Close();
+  Detach();

[Randy Smith (Not in Mondays), 2014/05/23 19:05:21]

Hmmm.  I'm a bit uncomfortable with the abstractions in this file; in my mind
"detached_" should mean "don't have anything to do with the underlying file
anymore" and nothing should be allowed to happen in that state (with the
possible exception of Rename(), but even there, it seems like that's a good
invariant to keep).  I.e once you've detached, destruction should be a no-op. 
That's larger (if still minor) cleanup, so I'm not requesting that you do it. 
But I think I would like the detach to be after the conditional, below.  

 
   if (!full_path_.empty()) {
     bound_net_log_.AddEvent(net::NetLog::TYPE_DOWNLOAD_FILE_DELETED);