# File lib/capybara/poltergeist/inspector.rb, line 35
    def self.browser_binary_exists?(browser)
      exts = ENV['PATHEXT'] ? ENV['PATHEXT'].split(';') : ['']
      ENV['PATH'].split(File::PATH_SEPARATOR).each do |path|
        exts.each { |ext|
          exe = "#{path}#{File::SEPARATOR}#{browser}#{ext}"
          return exe if File.executable? exe
        }
      end
      return nil
    end