Extension verification options not matching Chromium on Linux

[bsclifton]

Test plan

See brave/brave-core#8392

Description

Creating based on conversations / troubleshooting which took place in #2457

Basically, problem involves installing an extension which is signed but not in Chrome Web Store.

• Installing this component is not possible on macOS / Windows in Chromium. We properly match that behavior 👍
• However, Chromium on Linux WILL allow you to install. We are not allowing ☹️ Therefore not matching Chromium

Steps to Reproduce

• See [Desktop] Unable to install self-signed or third-party CRX extensions #2457 (comment) for detailed steps
• [Desktop] Unable to install self-signed or third-party CRX extensions #2457 (comment) also has notes for Linux

Actual result:

We don't match Chromium behavior

Expected result:

We should match Chromium behavior

Reproduces how often:

100%

Brave version (brave://version info)

Brave	1.24.32 Chromium: 90.0.4430.41 (Official Build) nightly (64-bit)
Revision	e9c92b1eaca8487e212f3f6bc081fdb6d4863759-refs/branch-heads/4430@{#723}
OS	Windows 10 OS Version 2009 (Build 19042.867)

Version/Channel Information:

• Can you reproduce this issue with the current release? Y
• Can you reproduce this issue with the beta channel? Y
• Can you reproduce this issue with the nightly channel? Y

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? N
• Does the issue resolve itself when disabling Brave Rewards? N
• Is the issue reproducible on the latest version of Chrome? N

[bsclifton]

Originally reported by folks in #5761 - apologies for not finding that (and creating this new issue). You can view lots of reports of the problem there from folks

[btlechowski]

The test plan from brave/brave-core#8392 involves all platforms. Added QA/Test-All-Platforms label.

[stephendonner]

Verified PASSED using slightly modified steps (checked with @bsclifton) from brave/brave-core#8392 on

Brave	1.25.60 Chromium: 90.0.4430.212 (Official Build) beta (x86_64)
Revision	e3cd97fc771b893b7fd1879196d1215b622c2bed-refs/branch-heads/4430@{#1429}
OS	macOS Version 11.3.1 (Build 20E241)

Steps:

1. New profile (macOS or Windows); launch Brave
2. Downloaded chromium-cleaner
3. Visited brave://extensions
4. Dragged the chromium-cleaner.crx extension from desktop onto the chrome://extensions page
5. Verified extension shows in brave://extensions as disabled (shows warning; you can't enable).
6. Repeated steps 4-6 while toggled in Developer mode; confirmed same (disabled) result

regular brave://extensions	Developer mode brave://extensions

---

Verification passed on

Brave | 1.25.60 Chromium: 90.0.4430.212 (Official Build) beta (64-bit)
-- | --
Revision | e3cd97fc771b893b7fd1879196d1215b622c2bed-refs/branch-heads/4430@{#1429}
OS | Windows 10 OS Version 2004 (Build 19041.985)

• Verified the test plan from Match Chromium behavior for extension loading brave-core#8392

Regular brave://extensions	Enable developer mode brave://extensions

---

Verification passed on

Brave	1.25.60 Chromium: 90.0.4430.212 (Official Build) beta (64-bit)
Revision	e3cd97fc771b893b7fd1879196d1215b622c2bed-refs/branch-heads/4430@{#1429}
OS	Ubuntu 18.04 LTS

• Verified the test plan from Match Chromium behavior for extension loading brave-core#8392

I was unable to install the extension when developer mode was off. Logged #15956

Installed the extension when developer mode was on:

[LaurenWags]

Changing release-notes/include to release-notes/exclude since Linux still does not work as expected and a follow up issue is logged (Unable to install self-signed extension when developer mode is off on Linux #15956).