Expand WebExtensions support

[aartaka]

Our current WebExtensions support is experimental, and there's not much extensions we can run with it. We need to expand it. We can start by supporting uBlock-required APIs, as this is a sane minimum for a WebExtensions support to have. Here's a (mostly copy-pasted from #1762) list of things to fix/add/think about:

• runtime.getURL returns data: URLs which are only suitable for resource loading, while being a security hole when navigated to. We need to use the recent mechanism from Internal schemes redesign. #2049 to build and fetch web-extension:// scheme links.
• Permissions
  • Implemented on Lisp-side.
  • Load-time ones on C-side.
  • Runtime change of permission on the C-side.
• Add/fix event filters. Commits between 9c942da and d9648bb add an experimental implementation of it, but it's unreliable and most likely broken.
• Commands.
• Option pages.
• Supporting more manifest.json keys (alphabetic order):
  • browser_action
  • content_scripts
  • description
  • homepage_url
  • icons
  • manifest_version
  • name
  • version
  • author
  • background
  • browser_specific_settings
  • chrome_settings_overrides
  • chrome_url_overrides
  • commands
  • content_security_policy
  • default_locale
  • developer
  • devtools_page
  • dictionaries
  • externally_connectable
  • incognito
  • offline_enabled
  • omnibox (set-url integration?)
  • optional_permissions
  • options_page
  • options_ui
  • page_action
  • permissions
  • protocol_handlers
  • short_name
  • sidebar_action
  • storage
  • theme (integrate with Enable color themes. #1889?)
  • theme_experiment
  • user_scripts (requires Support Greasemonkey user-scripts #2021?)
  • version_name
  • web_accessible_resources
• Supporting uBlock-used APIs (duplicated in Adblock/Umatrix like functionality? #32, will be tracked there from now on):
  • Methods (alphabetically, with unimplemented on top):
    • browser.browserAction.setPopup -- easy
    • browser.commands.getAll -- easy
    • browser.commands.reset -- easy
    • browser.commands.update -- easy
    • browser.i18n.getMessage -- easy?
    • browser.runtime.connect
    • browser.runtime.reload
    • browser.tabs.move -- easy
    • browser.webRequest.filterResponseData
    • browser.webRequest.handlerBehaviorChanged
    • browser.runtime.getBrowserInfo
    • browser.runtime.getManifest
    • browser.runtime.getURL
    • browser.tabs.create
  • Variables and types (will be mostly easy to do):
    • browser.runtime.lastError
    • browser.windows.WINDOW_ID_NONE -- easy
    • browser.webRequest.ResourceType -- easy
  • Events (alphabetically, with unimplemented on top, hardest to do as they require modifications all over Nyxt sources):
    • browser.browserAction.onClicked -- easy
    • browser.commands.onCommand -- easy
    • browser.runtime.onConnect
    • browser.runtime.onUpdateAvailable
    • browser.tabs.onActivated
    • browser.tabs.onCreated -- easy
    • browser.tabs.onRemoved -- easy
    • browser.tabs.onUpdated
    • browser.webNavigation.onCommitted
    • browser.webNavigation.onCreatedNavigationTarget
    • browser.webRequest.onBeforeRequest
    • browser.webRequest.onHeadersReceived
    • browser.windows.onFocusChanged -- easy
  • Non-mandatory but cool APIs because uBlock uses them to provide more features:
    • browser.dns
    • browser.privacy
    • browser.menus

[Ambrevar]

In #1762 you also mentioned:

Memory is not freed everywhere it needs to be. This can clutter our memory with time. Thus, C-side of things asks for more memory discipline.

Is this still valid?

[aartaka]

It's still valid, but it's not checkboxable and is an everpresent worry of mine. I think that we free most of the allocated resources now, so this is less relevant.