Disable flash in Tor

[yrliou]

Fix brave/brave-browser#1078
Flash is blocked by default right now, with this PR, users won't be able to enable it through content settings bubble or page info in Tor profile, so the settings should always stay blocked.
BTW, changing flash permissions in the normal profile won't be propagated to Tor profile either.

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Windows
  • macOS
  • Linux
• Verified that these changes pass automated tests (npm test brave_unit_tests && npm test brave_browser_tests) on
  • Windows
  • macOS
  • Linux
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone

Test Plan:

1. Open a new Tor window
2. Visit http://homestarrunner.com/main1.html
3. Click the plugin blocked bubble, there should be no "Run flash this time" and "Manage" button

4. Click the page info, there should be no flash entry to change permission.

5. Click on the flash element won't have any effect
6. Right click on the flash element, should not be able to click "Run this plugin"

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

[yrliou]

Works fine on mac, I'm building it on window & linux now to test.

[yrliou]

@bbondy This PR is ready for review, I can't do the manual test on linux though because flash seems to be not working on linux(brave/brave-browser#1562), but in theory I think this PR works for all platforms.

[simonhong]

LGTM

[simonhong]

Corresponding issue just said about blocking plugin.
Do we also want to hide location info in page info bubble?

[yrliou]

This is intentional cuz location permission is blocked in tor.

[simonhong]

Or, how about storing flash plugin & geolocation setting to ContentSettingsStore?
Chromium code base has a policy that user can't edit configuration set by extension by default.
With this, we don't need to disable/hide explicitly. WDYT?

[yrliou]

Or, how about storing flash plugin & geolocation setting to ContentSettingsStore?
Chromium code base has a policy that user can't edit configuration set by extension by default.
With this, we don't need to disable/hide explicitly. WDYT?

@simonhong I think it would be a bit weird that these default settings in Tor profile is "set by extension".
Especially that would be the message shown to users when they check the page info bubble.
We could probably use other providers that might make more sense, but I would prefer not to block this PR on how we set/store these settings and do it in a follow up since we also need to revise how we disable geolocation in Tor.
In any cases, I think the change in brave_content_setting_bubble_model.cc in this PR would still be needed.

[simonhong]

@yrliou Yeah, using appropriate providers seems make sense. My above comment is non-blocking comment. So you can go ahead with current one.

[bbondy]

master: 9aa3374
0.56.x: 236ff44
0.55.x: a2cdc86