Enable Web Serial by default

[ShivanKaul]

Description

We currently disable Web Serial by default, and allow enabling via flag. On looking at the user flow now, I don't see a reason to keep this disabled. Users get a permission popup and the API doesn't increase fingerprinting surface by default. Mozilla also changed their position recently; in Chromium Web Serial use requires a permission popup.

Steps to reproduce

Check status of brave://flags/#brave-web-serial-api

Actual result

Is off by default

Expected result

Should be on by default

Reproduces how often

Easily reproduced

Brave version (brave://version info)

1.68.40 Chromium: 125.0.6422.76 (Official Build) nightly (arm64) (I'm on Nightly but this is on all versions)

Channel information

• release (stable)
• beta
• nightly

Reproducibility

• with Brave Shields disabled
• with Brave Rewards disabled
• in the latest version of Chrome

Miscellaneous information

No response

[mkarolin]

Test plan:

1. Start Brave and navigate to permissions.site
2. Click on Serial button

Observe:
Permission prompt shows up.

3. Cancel from the permission prompt
4. Navigate to brave://settings/content
5. Click Additional permissions
6. Verify that Serial ports is listed

[mkarolin]

Note on deviation from the original description. Instead of making the flag enabled by default, the flag was removed entirely.

[stephendonner]

Verified PASSED using

Brave | 1.69.53 Chromium: 127.0.6533.17 (Official Build) nightly (x86_64)
-- | --
Revision | bedcc2e74ce45bd641d2946e0d870d68ba08b8e9
OS | macOS Version 11.7.10 (Build 20G1427)

Steps:

1. installed 1.69.53
2. launched Brave
3. opened brave://flags
4. searched for serial
5. confirmed no matching flags
6. loaded permission.site
7. clicked on Serial
8. confirmed permissions prompt
9. clicked on Connect for the first highlighted entry
10. confirmed the Serial button on the page turned green (enabled)
11. clicked again on Serial

Confirmed Web Serial was enabled by default, has no flag, and I could successfully pair

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