* Move TextSourceRange static functions to DocumentUtil
getWritingMode is also simplified
* Update Google Docs range to be empty to match other range sources
* Rename imposterContainer to imposterElement
* Add static creation functions
* Add static creation function
* Remove unused collapse function
* Don't select imposter elements
* Refactor setEndOffset
* Adjust argument order for setEndOffset
* Update TextSourceRange constructor
* Remove unused isConnected
* Cache rects
* Fix test
* Remove unused getRect
* Revert "Fix test"
* Remove cachedRect
* Use the source element rect to handle scroll differences
* Writing mode update
* Remove _cachedRects update
This shouldn't be necessary as the imposter is usually detached
almost immediately after scanning, giving no time for the window
to be resized or scrolled.
* Skip urlRegex if it's used as a filter
* Add getRequiredContentScriptRegistrationPermissions function
* Add a reentrant check to google-docs.js
* Remove script node
* Move forceGoogleDocsHtmlRendering check into google-docs.js
* Replace document-start.js usage with google-docs.js
* Remove documentStart handling
* Add missing parameter descriptions
* Add accessibility option for forcing Google Docs HTML-based rendering
* Update settings
* Send a documentStart message at document start
* Add accessibility script for Google Docs
* Set up accessibility
* Update tests
