Fix #7574: Add support for multi-window & persistent private browsing

[Brandon-T]

Security Review

• https://github.com/brave/reviews/issues/1329

Summary of Changes

• Add support for multi-window
• Add "Open In New Window" and "Open In New Private Window" context menu when long-pressing on a link.
• Add support for persistent private browsing (coming in a separate "commit").
• Added support for Persistent Private Browsing (via a toggle in Privacy Settings), so private tabs can be session restored like Safari and all other browsers.
• Private Browsing ONLY mode will automatically disable persistent private browsing!
• Tabs do NOT save in PBO mode! Turning off PBO will still wipe all your tabs.
• Turning off Persistent Private Browsing (PPB) will not wipe your tabs, but it will wipe them from DISK. So killing the app will not restore them.

TODO:

• Need a better way to "open a new window" (instead of long-pressing the plus sign, but that's about it, and does not block review).

This pull request fixes #7574

Submitter Checklist:

• Unit Tests are updated to cover new or changed functionality
• User-facing strings use NSLocalizableString()
• New or updated UI has been tested across:
  • Light & dark mode
  • Different size classes (iPhone, landscape, iPad)
  • Different dynamic type sizes

Test Plan:

• Test every feature
• Test private browsing for everything

Screenshots:

Split (Regular + Regular):

Split (Regular + Private):

Private Window Protection:

Private Window NTP:

Reviewer Checklist:

• Issues include necessary QA labels:
  • QA/(Yes|No)
  • bug / enhancement
• Necessary security reviews have taken place.
• Adequate unit test coverage exists to prevent regressions.
• Adequate test plan exists for QA to validate (if applicable).
• Issue and pull request is assigned to a milestone (should happen at merge time).

[kylehickinson]

Runtime Review:

Prefix: These were all tests based on having 2 windows of Brave side-by-side on a 12.9" iPad in landscape orientation

Bugs That Need Fixing:

• Brave News: Turning on Brave News on one windows NTP breaks Brave News on the other window

  • Expected: News should load on the other window as well and display the same data set

• Brave News: Altering followed sources only brings up "New Content Available" button on window that triggered it. Closing a tab on another window doesn't reload Brave News with the new set of data and will not show the updated data until the app is killed and re-launched.

  • Expected: Both NTPs should reference the same set of News data or at least ensure that new NTP's use the updated data

• Browser Lock: "Unlock" button only appears on 1 window until its tapped on the other?

  • Expected: Should show it on both probably

• Playlist: Plays the same content on multiple windows

  • Expected: If content can only be played on one window at a time then we need to block the other or something with some UI

• Playlist: Shows "Resource Loading" errors when playing from multiple windows

Polish:

• Shields: Turning shields off for a website loaded in multiple windows does not reflect that

  • Expected: Sync state across windows, reload matching webpages on all connected scenes?

• Brave News: Toggling follow status of a source while viewing the source window on both windows don't update until you leave and revisit the screen

  • Expected: If possible these should be synced so that changes to the

• Browser Lock: Unlocking from browser lock only unlocks one window. Intended behaviour?

  • Expected: Unlock all scenes that are connected/visible on the screen/foregrounded

• Playlist: Removing an item from Playlist doesn't update the URL bar if you're viewing the videos source webpage at the same time

  • Expected: Should stay in sync so that items added/removed from one window sync to the other

• Tab Tray: For some reason if you open the tab tray on one window and click on the other window, the cells aspect ratio changes.

  • Expected: I assume the longer one is the correct one but not sure

[kylehickinson]

This PR may as well been named "Remove PrivateBrowsingManager singleton, oh and by the way also add multi-window support" 😂

[Brandon-T]

Bugs That Need Fixing

• Fixed Brave-News not syncing across windows by using the same data-source for all (fixes all the Brave-News issues mentioned).
• Fixed playlist url bar not syncing across windows when watching the same video in two windows, and adding/removing from playlist in one of the windows.
• Fixed turning off/on shields on one window with the same tab open on another window, not syncing across windows. This one was weird to fix, because technically turning off the shields on one tab ("youtube" for example), would NOT reload all the "youtube" tabs that are open. It only ever reloaded the "selected" tab. But I fixed it so it reloads ALL of the tabs that are of the same domain, across ALL of the windows. I wasn't sure of the behaviour :D so I went with reloading all.

Not sure:
I'm not sure how the Browser-Lock should behave tbh.
For example, what if I locked one window because it's private, but then leave another window unlocked? Or what if I minimized one window which causes it to lock, it shouldn't lock the other window that's in the foreground, so I would expect to unlock each window?

Also, I left playlist working on multiple windows because I realized this is what Safari and WebKit do when you're playing Youtube on multiple web-views. So I followed the same behaviour. Though, I could always block it I guess.

[aguscruiz]

I have the design for private tabs lock available here:
https://www.figma.com/file/6KPhbe8yqCPOLgFT2AYlju/Private-nav---Application-lock?type=design&node-id=235%3A9849&mode=design&t=ny7nqJqyW1dNCDqw-1

[iccub]

Thanks @aguscruiz.
This is however separate from what's left for this PR which is a small alert telling existing users whether they want to persist their tabs or not