Private window Shields toggle doesn't update panel

[antonok-edm]

STR:

1. Visit https://example.com or any other site in a normal tab
2. Open the Shields panel
3. Turn Shields down
4. Open a new Private window
5. Visit the same website in the Private window
6. Open the Shields panel
7. Toggle Shields a few times
8. Observe that the panel text and appearance does not change whenever Shields is up

[boocmp]

Well....

When enabling shields on a page, it triggers a call to brave_shields::ResetBraveShieldsEnabled, which sets the CONTENT_SETTING_DEFAULT value in HostContentSettingsMap.

For normal profiles, this works fine because when BRAVE_SHIELDS content setting contains CONTENT_SETTING_DEFAULT (indicating no explicit value is set), GetBraveShieldsEnabled returns true - the expected default value.

However, for off-the-record HostContentSettingsMap, the behavior differs. If no value exists in the off-the-record copy, it falls back to the normal profile's value, leading to unexpected behavior with the default setting.

To fix this, we should explicitly set the value (even if it matches the default) in the incognito HostContentSettingsMap.

A review of brave_shields_util.cc reveals many settings using this same logic. It seems all such instances will need to be updated for consistency.

[ShivanKaul]

If no value exists in the off-the-record copy, it falls back to the normal profile's value, leading to unexpected behavior with the default setting.

Why can't it fall back to the default value? And then be toggled separately? I think I'm missing something.

A review of brave_shields_util.cc reveals many settings using this same logic. It seems all such instances will need to be updated for consistency.

Which other ones? The fingerprint toggle for e.g. looks like it works correctly in Regular vs Private Window.

[boocmp]

It's a content settings logic, default values for incognito defined as values in original content settings, we just keep it in mind in future.

It may looks like it works correctly, but we need to write the concrete test to be sure.

[boocmp]

I found other settings that could fail to be set in incognito for some values in the regular profile. But these values are not accessible from UI, so I've added DCHECK-s into the corresponding setters.