site banner should have 'on YouTube' text when appropriate

[LaurenWags]

Description

When you go to tip a YouTube channel, the site banner now says the channel name and displays channel favicon. However, site banner does not indicate that the site is 'on YouTube' as it does on the Brave panel (when you click on BAT logo) or on the Brave Rewards page (in AutoContribute table).

Steps to Reproduce

1. If not already enabled, enable Brave Rewards.
2. Navigate to https://www.youtube.com/channel/UCFNTTISby1c_H-rm5Ww5rZg
3. View a video.
4. Click on BAT logo. Note that you see 'on YouTube' text on the panel.
5. Click on Send a Tip

Actual result:

Site banner displays, but does not have 'on YouTube' text:

Expected result:

Site banner should note 'on YouTube' to be consistent with Brave panel and Brave Rewards page.

Reproduces how often:

easily

Brave version (brave://version info)

Brave	0.57.7 Chromium: 71.0.3578.53 (Official Build) beta(64-bit)
Revision	599fb72e740eab9d10609f1ed28a2ad669f82c1a-refs/branch-heads/3578@{#669}
OS	Mac OS X

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds? yes

Website problems only:

• Does the issue resolve itself when disabling Brave Shields? n/a
• Is the issue reproducible on the latest version of Chrome? n/a

Additional Information

The 'on YouTube' text also displays on the brave://rewards page:

[LaurenWags]

Verified passed with

Brave	0.59.12 Chromium: 72.0.3626.17 (Official Build) beta(64-bit)
Revision	08d2140079f8db14c9eb885a803d231b1a30e817-refs/branch-heads/3626@{#315}
OS	Mac OS X

Verification passed on

Brave	0.59.12 Chromium: 72.0.3626.17 (Official Build) beta (64-bit)
Revision	08d2140079f8db14c9eb885a803d231b1a30e817-refs/branch-heads/3626@{#315}
OS	Windows 10

Verification passed on

Brave 0.59.12 Chromium: 72.0.3626.17 (Official Build) beta (64-bit)
Revision 08d2140079f8db14c9eb885a803d231b1a30e817-refs/branch-heads/3626@{#315}
OS Linux