Wikimedia Bugzilla is closed!

Reverted https://gerrit.wikimedia.org/r/#/c/104783/ because it requires that the BROWSER_LABEL environment variable be set, and this is not always true.  

Instead, we should use the local definition of browser_label from support/env.rb:

def local_browser(user_agent)
  if ENV['BROWSER_LABEL']
    browser_label = ENV['BROWSER_LABEL'].to_sym
  else
    browser_label = :firefox
  end

This requires making the browser_label variable available beyond the scope of of the local method.