[Downloads] Retry renames after transient failures.

content/browser/download/download_stats.cc

Index: content/browser/download/download_stats.cc
diff --git a/content/browser/download/download_stats.cc b/content/browser/download/download_stats.cc
index 66716cac415d555be3af8e34fe8e437c8f137702..d88eef2c4e2c039e61add7820cc94b88b562cfbe 100644
--- a/content/browser/download/download_stats.cc
+++ b/content/browser/download/download_stats.cc
@@ -611,6 +611,18 @@ void RecordFileBandwidth(size_t length,
                            disk_write_time_ms * 100 / elapsed_time_ms);
 }
 
+void RecordDownloadFileRenameResultAfterRetry(
+    base::TimeDelta time_since_first_failure,
+    DownloadInterruptReason interrupt_reason) {
+  if (interrupt_reason == DOWNLOAD_INTERRUPT_REASON_NONE) {
+    UMA_HISTOGRAM_TIMES("Download.TimeToRenameSuccessAfterInitialFailure",
+                        time_since_first_failure);
+  } else {
+    UMA_HISTOGRAM_TIMES("Download.TimeToRenameFailureAfterInitialFailure",
+                        time_since_first_failure);
+  }

[Randy Smith (Not in Mondays), 2014/06/11 18:07:29]

I may be a missing a corner case of the math, but at first glance I feel like
these UMA don't give us everything we need to evaluate what's going on;
specifically, I don't think they tell us how often the initial rename failed. 
We'll only get success results for renames that don't fall off the end of the
retry count, so we won't be able to tell the difference between (e.g.) some 2x
retries and no never-succeeded, and many never succeeded and some 1x retries.  

[asanka, 2014/06/12 20:02:37]

This stat is recorded whenever we retry a rename regardless of the final
outcome. The final outcome determines which histogram is updated. So, some 2x
retries and no never-succeeded:

Download.TimeToRenameSuccessAfterInitialFailure
Time(ms) \ Frequency:
000 :
200 :
300 : 
400 : ####
500 : ##
600 : 
700 :
800 :

Download.TimeToRenameFailureAfterInitialFailure
Time(ms) \ Frequency:
000 :
200 :
300 :
400 :
500 :
600 :
700 :
800 :

Many never succeeded and some 1x retries:

Download.TimeToRenameSuccessAfterInitialFailure
Time(ms) \ Frequency:
000 :
200 : ####
300 : #
400 : 
500 : 
600 : 
700 :
800 :

Download.TimeToRenameFailureAfterInitialFailure
Time(ms) \ Frequency:
000 :
200 :
300 :
400 :
500 :
600 :
700 :
800 : #######################################

+}
+
 void RecordSavePackageEvent(SavePackageEvent event) {
   UMA_HISTOGRAM_ENUMERATION("Download.SavePackage",
                             event,