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-by: Tatsuhisa Yamaguchi <>
Commit-Queue: Naoki Fukino <>
Cr-Original-Commit-Position: refs/heads/master@{#536980}(cherry picked from commit 33e085fe31cc14110fc52092a35ee84c412b6bbb)
Reviewed-by: Naoki Fukino <>
Cr-Commit-Position: refs/branch-heads/3325@{#528}
Cr-Branched-From: bc084a8b5afa3744a74927344e304c02ae54189f-refs/heads/master@{#530369}
1 file changed