* Remove unnecessary load of /fg/css/client.css
* Replace dynamicLoader.loadStyles with dynamicLoader.loadStyle
* Replace Popup._injectStylesheet with dynamicLoader.loadStyle
* Remove unused global
* Add default
* Convert function to non-static
* Remove static for private functions
* Replace .call
* Move functions with side effects into a synchronous prepare function
* Rename variables with "container" to "frame" in _initializeFrame
* Rename variables with "container" to "frame"
* Rename getContainer to getFrame
* Rename getContainerRect to getFrameRect
* Organize and simplify
* Fix incorrect change of "popup" => "this"
* Move initial _updateVisibility into prepare()
* Rename PopupProxyHost to PopupFactory
* Update FrontendApiReceiver to support non-async handlers
* Make some functions non-async
* Make setCustomCss non-async
* Make setContentScale non-async
* Remove static
* Rename variables
* Pass frameId into PopupFactory's constructor
* Change FrontendApiReceiver source from popup-proxy-host to popup-factor
* Rename _invokeHostApi to _invoke
* Rename PopupProxy.getHostUrl to getUrl
* Add API function to send a message to a specific frameId in a tab
* Update _windowMessageHandlers to support additional info per handler
* Remove message token
* Add new authorization check
* Set up new initialization handler
* Update initialization
* Remove message token
* Replace 'prepare' with 'configure'
* Create new prepare function
* Change configure guard
* Log errors in onMessage
* Improve popup initialize function
* Clear secret/token in _resetFrame
* Remove backend message token
* Clear src and srcdoc attributes before loading
* Don't treat about:blank unloads as load events
* Validate document.body before use in loadScripts
This also fixes an issue where reject wasn't being passed to loadScriptSentinel.
* Validate document nodes before use in _getSiteColor
* Validate document.body before use in _getViewport
* Validate document.body before use in setContentScale
* Validate document.body before use in docImposterCreate
* Remove and unload the popup frame if an unexpected load occurs
* Remove unused fields
* Only update _injectPromiseComplete if the promise is the most recent one
* Remove redundant this._injectPromise !== null check
* set optionsContext from Frontend
* update Popup+Display options on Frontend change
* remove popup setOptions
* only update DisplayFloat options from Frontend
* fix optionsContext usage
* fix preview frame arguments
* keep Frontend URL up to date
* cache url
* fix preview frame
* trigger modifyingProfileChange in correct places
* remove async from function not using await
* refactor optionsContext in Frontend
