Fix regression in #20017: wrong number of arguments error

and use coherent quoting/spacing.

This should hopefully fix a regression that was introduced with #20017,
causing deployment pushes to Heroku to be rejected with the following
trace:

ArgumentError: wrong number of arguments (2 for 3)
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/actionpack/lib/action_dispatch/middleware/s
tatic.rb:16:in `initialize'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/gem
s/heroku-deflater-0.5.3/lib/heroku-deflater/serve_zipped_assets.rb:15:in
`new'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/gem
s/heroku-deflater-0.5.3/lib/heroku-deflater/serve_zipped_assets.rb:15:in
`initialize'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/actionpack/lib/action_dispatch/middleware/s
tack.rb:43:in `new'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/actionpack/lib/action_dispatch/middleware/s
tack.rb:43:in `build'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/actionpack/lib/action_dispatch/middleware/s
tack.rb:118:in `block in build'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/actionpack/lib/action_dispatch/middleware/s
tack.rb:118:in `each'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/actionpack/lib/action_dispatch/middleware/s
tack.rb:118:in `inject'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/actionpack/lib/action_dispatch/middleware/s
tack.rb:118:in `build'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/railties/lib/rails/engine.rb:509:in `app'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/railties/lib/rails/application/finisher.rb:
34:in `block in <module:Finisher>'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/railties/lib/rails/initializable.rb:30:in
`instance_exec'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/railties/lib/rails/initializable.rb:30:in
`run'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/railties/lib/rails/initializable.rb:55:in
`block in run_initializers'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/railties/lib/rails/initializable.rb:54:in
`run_initializers'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/vendor/bundle/ruby/2.2.0/bun
dler/gems/rails-0ef7e73f0af7/railties/lib/rails/application.rb:352:in
`initialize!'
remote:
/tmp/build_a3b8845b716508af12d99859d1a58c5c/config/environment.rb:5:in
`<top (required)>'

actionpack/lib/action_dispatch/middleware/static.rb

@@ -13,7 +13,7 @@ module ActionDispatch
   # located at `public/assets/application.js` if the file exists. If the file
   # does not exist, a 404 "File not Found" response will be returned.
   class FileHandler
-    def initialize(root, cache_control, index)
+    def initialize(root, cache_control, index = 'index')
       @root          = root.chomp('/')
       @compiled_root = /^#{Regexp.escape(root)}/
       headers        = cache_control && { 'Cache-Control' => cache_control }
@@ -105,7 +105,7 @@ module ActionDispatch
   # produce a directory traversal using this middleware. Only 'GET' and 'HEAD'
   # requests will result in a file being returned.
   class Static
-    def initialize(app, path, cache_control=nil, index="index")
+    def initialize(app, path, cache_control = nil, index = 'index')
       @app = app
       @file_handler = FileHandler.new(path, cache_control, index)
     end
@@ -115,7 +115,7 @@ module ActionDispatch
       when 'GET', 'HEAD'
         path = env['PATH_INFO'].chomp('/')
         if match = @file_handler.match?(path)
-          env["PATH_INFO"] = match
+          env['PATH_INFO'] = match
           return @file_handler.call(env)
         end
       end