Issue 758682  has been merged into this issue.

IIUC this is working as intended.
As I wrote in  issue 740063 , this means there is no application which can handle the said file types.
After installing an appropriate application (e.g. Microsoft Office), you'll be able to open the files with it.

Do you mean a Chrome OS device should be able to open these files by default?

Re #2, I had appropriate android apps installed to open/share the said file types like VLC for Android, MS word, Google Photos android app, Gmail app, FB app etc. As you can see from the bug description, I could open/share the same set of files from Downloads/Gdrive/Recent/External drive using ARC++ apps but not from MTP/FSP/Media folders.

Do you mean a Chrome OS device should be able to open these files by default?
>> No, I was not referring to ChromeOS default apps.

Could you provide more concrete examples (i.e. actual combinations of file name, file location, and Android app)?

I tried to reproduce this, but I couldn't.
I tried opening a PDF file whose name ends with ".pdf" in Downloads, Google Drive, and in a Nexus 7 connected via MTP, with Drive PDF viewer (which is part of Google Drive app), and all succeeded on an eve device (Platform 10445.0.0).

Sorry if I was not clear about the issue. Referring to Additional info from the bug description:

1. Open/Share feature works fine for file types such as PDF, Audio file, Images formats (like PNG, JPEG) from MTP/FSP.

2. Open/Share feature also works fine for files in Downloads, Gdrive, Recent, External drive.

*** Main issue here is 
UNABLE to Open/Share file types - Video, raw images, MS Docs from MTP, FSP directories. Where as opening/ sharing the same set from Downloads, GDrive works fine with ARC++ apps.

*** Another issue to mention is 
The files from Media folders (Images, Videos, Audio) don't have Open/Share support with ARC++ apps.

Please refer the issue video attached:
https://pantheon.corp.google.com/storage/browser/chromiumos-test-logs/bugfiles/cr/816678/

OK, finally understood what this issue is about, thanks.

When filing bugs next time, could you provide more concrete repro steps?
For example:
 1. Install "File System for Dropbox" from Chrome Web Store and log in to a Dropbox account.
 2. Install Google Photos app from Play store.
 3. Prepare a .cr2 file in the Dropbox directory.
 4. Try to open the .cr2 file with Photos.

This would be much easier than figuring out what "certain android apps" and "a raw image/video file (other than MP4 format)" mean, and it would allow everyone to repro the said issue quickly.
Thanks!

(Removing RVG as there is nothing confidential)

It seems certain types of files (e.g. raw image files whose extension is ".cr2") are not properly handled in MTP/FSP/Media directories.
Probably, it's failing to guess the MIME type from the file extension?
Do we have a list of file types which we need to be able to handle with Android applications?

fukino@, who is the right person to handle this?

+sashab@ - FYI as we transition over. Not sure if this is something we'll get to in M67.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f8ad0975f1c66b384f3bbb6ccd93b3831e0d98d3

commit f8ad0975f1c66b384f3bbb6ccd93b3831e0d98d3
Author: Satoshi Niwa <niwa@google.com>
Date: Mon Apr 02 04:56:05 2018

Migrate file_manager/arc_file_tasks to using async version of ConvertToContentUrls

Bug: chromium:811679
Bug:  chromium:816678 
Bug: b:76128680
Test: Manually tested steps in b:76128680

Change-Id: Ia997588424e90af97aac2f89de1fe1e84266b6fc
Reviewed-on: https://chromium-review.googlesource.com/987634
Reviewed-by: Shuhei Takahashi <nya@chromium.org>
Reviewed-by: Daichi Hirono <hirono@chromium.org>
Commit-Queue: Satoshi Niwa <niwa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547411}
[modify] https://crrev.com/f8ad0975f1c66b384f3bbb6ccd93b3831e0d98d3/chrome/browser/chromeos/file_manager/arc_file_tasks.cc
[modify] https://crrev.com/f8ad0975f1c66b384f3bbb6ccd93b3831e0d98d3/chrome/browser/chromeos/file_manager/arc_file_tasks.h
[modify] https://crrev.com/f8ad0975f1c66b384f3bbb6ccd93b3831e0d98d3/chrome/browser/chromeos/file_manager/file_tasks.cc

I think this issue is resolved by the CL above.

Right-clicking on a file in a ARC media directory now shows "Open with..." and "More actions..." menus linking to ARC apps(e.g. Astro File Manager)

mkarkada@, please verify once crrev.com/c/987634 reaches ToT.