Application Version (from "Chrome Settings > About Chrome"): 56.0.22924.18
Android Build Number (from "Android Settings > About Phone/Tablet"): N2F62
Device: Pixel

Steps to reproduce: 
1) Visit a "bare" JPEG image directly using a URL, e.g., 
https://blogintomystery.files.wordpress.com/2010/07/atlas.jpg

2) Tap three dots menu

3) Tap Download button on first row of the menu

4) See "blogintomystery.files.wordpress.com downloaded"

5) Tap "Open" in the snackbar

Observed behavior: 

A few problems here:

1) When opening the downloaded image, the snack bar shows up "Viewing an offline copy of this page". This suggests that Chrome is treating the bare JPEG that I downloaded as an offline page, rather than just an image.

2) The downloaded image does not appear in the Android "Downloads" app. Meaning, the image cannot be read by other apps (e.g., Facebook, WhatsApp, ShareIt) for sharing *from within those apps*.

3) Now that long-pressing on an image and selecting "Download image" will save it to, e.g., file:///storage/emulated/0/Download/atlas.jpg which means that the image *is* visible to other apps for sharing.

Expected behavior:

I believe tapping the download button in the three-dots menu and long-pressing an image and selecting "Download image" should do the same thing.