Block Scripts and Fingerprinting Protection not working when open a guest/tor window multiple times

[jumde]

Test plan

See #1381 (comment)

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POC: http://peltate-worth.000webhostapp.com/world.html

Version:
0.55.10 Chromium: 70.0.3538.22 (Official Build) beta (64-bit)

[yrliou]

STR:

1. Open a guest window and close it
2. Open a guest window again
3. Open http://peltate-worth.000webhostapp.com/world.html and click block scripts in shields
4. the script blocking is not working as expected, shield icon is gray out

Shields stop working correctly for scripts and fingerprinting protection (ads/trackers still work, I didn't test others) after we open a guest / tor window for the second time.
Things seem to be back to normal after toggle the shield on/off switch or restart the browser

[yrliou]

BraveContentSettingsObserver::IsBraveShieldsDown return true when this bug happens, that's why script blocking and fingerprinting protection settings has no effect because it thinks shields is down.

[srirambv]

@yrliou #1381 (comment) is similar to #1437?

[yrliou]

@srirambv Seems different and I can't reproduce #1437 on 0.56.2 (macos).

[yrliou]

We lost those brave default rules (especially the braveShields one) which only be set once when init HostContentSettingsMap, I think this issue will also be resolved by brave/brave-core#622.

[yrliou]

Test Plan:

1. Open a guest window and close it
2. Open a guest window again
3. Open http://peltate-worth.000webhostapp.com/world.html, click on "Show Message" will show an alert window.
4. Click block scripts in shields
5. The scripts should be blocked, make sure clicking on "Show Message" will have no alert window
   Fingerprinting
6. Open a new tab and navigate to https://browserleaks.com/canvas
7. Open the shield panel and set fingerprinting protection to block all
8. Fingerprinting should be blocked and the page should be shown as below

9. Open a tor window and close it
10. Open a tor window again
11. Repeat step 3 to step 8

[srirambv]

Verification Passed on

Brave	0.55.16 Chromium: 70.0.3538.54 (Official Build) (64-bit)
Revision	4f8e578b6680574714e9ed3bb9f02922b4dde40d-refs/branch-heads/3538@{#937}
OS	Linux

Verification Passed on

Brave	0.55.16 Chromium: 70.0.3538.54 (Official Build) (64-bit)
Revision	4f8e578b6680574714e9ed3bb9f02922b4dde40d-refs/branch-heads/3538@{#937}
OS	Windows

Verified passed with

Brave	0.55.17 Chromium: 70.0.3538.67 (Official Build) (64-bit)
Revision	9ab0cfab84ded083718d3a4ff830726efd38869f-refs/branch-heads/3538@{#1002}
OS	Mac OS X

*Verified test plan from #1381 (comment)