Errors/warnings seen when changing Shields settings from panel

[mariospr]

Description

As mentioned in #6828 (comment), I'm seeing the following kind of errors on today's build off the master branch (Brave 1.20.28 - based on Chromium 88.0.4315.5), whenever I change any of the Shields's settings for the current website, from the Shields panel:

[2697829:2697829:1215/182658.592733:WARNING:render_widget_host_impl.cc(267)] Input request on unbound interface
[2697829:2697829:1215/182700.174136:WARNING:CONSOLE(20063)] "%cWarning: a promise was created in a handler at /mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js:2390:45 but was not returned from it, see http://goo.gl/rRqMUw
    at new Promise (chrome-extension://mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js:21221:10)
    at reloadTab (chrome-extension://mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js:1143:43)
    at chrome-extension://mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js:2390:45
From previous event:
    at shieldsPanelReducer (chrome-extension://mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js:2389:18)
    at combination (chrome-extension://mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js:25197:29)
    at dispatch (chrome-extension://mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js:24957:22)
    at Object.dispatch (chrome-extension://mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js:2020:16)
    at dispatchResponse (chrome-extension://mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js:26616:32)
    at chrome-extension://mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js:25904:25 color: darkorange", source: chrome-extension://mnojpmjdmbbfmejpflffifhffcmidifd/out/brave_extension_background.bundle.js (20063)

Steps to Reproduce

1. Launch Brave from the terminal (e.g. npm run brave)
2. Open a website and wait until finishes loading
3. Open the Shields panel and change any option (e.g. enable or disable "Script blocking")
4. Look into the output in the terminal window

Actual result:

Errors such as the ones pasted above are seen whenever Shields' settings are changed

Expected result:

No errors should show up when changing Shields' settings.

Reproduces how often:

Always

Desktop Brave version:

Brave 1.20.28 (based on Chromium 88.0.4315.5)

Version/Channel Information:

So far I only reproduced it with the nightly channel (master)

Other Additional Information:

Doesn't seem to be causing any actual problem with Shields.