Now that autoplay policy has changed, the autoplay function in quick view has stopped working.
https://developers.google.com/web/updates/2017/09/autoplay-policy-changes

To preview video files in Files app's quick view, we use <video> tag with "autoplay" attribute.
(i.e. <video autoplay src=...>)
For security reason, we load a document containing the video tag inside <webview> tag. It seems the policy change affect the video tag inside <webview>.

+hanxi@, lfg@ from components/guest_view OWNERS.
Is there a way to enable autoplay in <webview>?

According to https://developers.google.com/web/updates/2017/09/autoplay-policy-changes#iframe, we can delegate autoplay permission to our iframes to allow autoplay.
But I'm not sure if we have similar options on <webview>.

Given the policy update - let's proceed with enabling muted auto-play for M65.

I am no longer working on gurest_view, +paulmeyer@ and wjmaclean@ for opinions.

If this is due to a purposeful policy change, I don't think it should be labelled as a regression. Since this bug is turning into a feature request, let's relabel it as such.

For M65, we are going with muted autoplay for video preview function.
After a patch for muted autoplay lands, I'll keep this bug open as a feature request to enable unmuted autoplay by delegating permission to the iframe in <webview>.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/33e085fe31cc14110fc52092a35ee84c412b6bbb

commit 33e085fe31cc14110fc52092a35ee84c412b6bbb
Author: Naoki Fukino <fukino@chromium.org>
Date: Thu Feb 15 09:57:21 2018

Files app: Enable muted autoplay for previewing video files.

Due to a Chrome policy change, autoplaying videos does not work in quick view.
Instead, we introduce muted autoplay to help users preview video files.

Bug: 804273
Test: Manually tested.
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I07768b04ff3994f53811d22fd33613291dd5b896
Reviewed-on: https://chromium-review.googlesource.com/920049
Reviewed-by: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Commit-Queue: Naoki Fukino <fukino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536980}
[modify] https://crrev.com/33e085fe31cc14110fc52092a35ee84c412b6bbb/ui/file_manager/file_manager/foreground/elements/files_safe_video_webview_content.html

I'd like to merge the patch in comment #8 to M65.

This issue will be perceived as a regression from users.
The fix in comment #8 mitigate the issue, with extremely low risk.

The bug is marked as P3 or Feature. It should not be merged as M65 is in beta. 
Please contact the approriate milestone owner if you have questions.
Owners: cmasso@(Android), cmasso@(iOS), bhthompson@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

It is actually a regression from the users' standpoint.
Let me get the type back to Regression and re-request a merge.

Once the mitigation in comment #8 is merged, I'll change the issue type to Feature to pursuit further improvement.

This bug requires manual review: M65 has already been promoted to the beta branch, so this requires manual review
Please contact the milestone owner if you have questions.
Owners: cmasso@(Android), cmasso@(iOS), bhthompson@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4ac90930492bd8b71f56796f78c63e21faf7e45e

commit 4ac90930492bd8b71f56796f78c63e21faf7e45e
Author: Naoki Fukino <fukino@chromium.org>
Date: Wed Feb 21 09:03:17 2018

Files app: Enable muted autoplay for previewing video files.

Due to a Chrome policy change, autoplaying videos does not work in quick view.
Instead, we introduce muted autoplay to help users preview video files.

Bug: 804273
Test: Manually tested.
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I07768b04ff3994f53811d22fd33613291dd5b896
Reviewed-on: https://chromium-review.googlesource.com/920049
Reviewed-by: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Commit-Queue: Naoki Fukino <fukino@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#536980}(cherry picked from commit 33e085fe31cc14110fc52092a35ee84c412b6bbb)
Reviewed-on: https://chromium-review.googlesource.com/928062
Reviewed-by: Naoki Fukino <fukino@chromium.org>
Cr-Commit-Position: refs/branch-heads/3325@{#528}
Cr-Branched-From: bc084a8b5afa3744a74927344e304c02ae54189f-refs/heads/master@{#530369}
[modify] https://crrev.com/4ac90930492bd8b71f56796f78c63e21faf7e45e/ui/file_manager/file_manager/foreground/elements/files_safe_video_webview_content.html

The mitigation (introducing muted autoplay for videos) has landed.

Changing the bug type as a Feature to re-enable the autoplay with sound in quick view.
Let me release this bug to find another owner for the improvement.

Removing Blink>Media>Autoplay, please re-add if there's an issue with the policy

Weifang - please advise on the priority for this? :)

We can keep this as a P3 for now and revisit when we are looking to clean up/improve Quick View.