Address some review comments.
Remove legacy code.
Expose `getActiveBrowser` that can be shared across tabs and windows.
Remove all the platform specific code branching for windows.
Update dependencies.
Add more comments.
Get rid of platform specific code branching.
Make iterator configurable.
Expose function with a more descriptive name.
Fix tab model.
Fix requirements in tabs module.
Implements tab getter.
Add missing dependencies.
Fix requirement paths.
Add tab utility modules.