[Desktop] Give a visual indicator that DRM is in use

[initsecret]

Description

Provide a visual indicator to the user that DRM software is in use.

Steps to Reproduce

1. Navigate to https://bitmovin.com/demos/drm
2. If not already allowed, allow widevine

Actual result:

Expected result:

Show a visual indicator like Firefox.

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Brave	1.15.4 Chromium: 85.0.4183.78 (Official Build) nightly (64-bit)
Revision	720ec01a54ea94d2d8b7a1d273e0fa89722fb11b-refs/branch-heads/4183@{#1603}
OS	Windows 10 OS Version 2004 (Build 19041.450)

Version/Channel Information:

Can reproduce this in nightly and in the current release.

Miscellaneous Information:

#2791 is related, these issues could share the same UI.