Extend the expiry of several download metrics.

This CL extends expiry of several metrics related to download and media.

Useful for implementing new feature:
Android.DownloadManager.ViewRetentionTime.Video
Android.DownloadManager.ViewRetentionTime.Audio
Download.DeleteRetentionTime.Video
Download.DeleteRetentionTime.Audio

Important system health metrics:
Download.ParallelDownloadAddStreamSuccess
Download.ParallelDownloadRequestCount

Bug: 918380,918378
Change-Id: Id597b9a8ae3ed72f1c0b0cd95ef36df4b5467d8d
Reviewed-on: https://chromium-review.googlesource.com/c/1428741
Reviewed-by: Min Qin <qinmin@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625377}
1 file changed