optimize newing up the builder

autoload/airline.vim

@@ -48,9 +48,7 @@ function! airline#get_statusline(winnr, active)
     endif
   endif
 
-  let info = builder.build()
-  call setwinvar(a:winnr, 'airline_current_info', info)
-  return info.statusline
+  return builder.build()
 endfunction
 
 function! airline#update_statusline()

autoload/airline/builder.vim

@@ -1,29 +1,25 @@
 " MIT license. Copyright (c) 2013 Bailey Ling.
-" vim: et ts=2 sts=2 sw=2 fdm=indent
+" vim: et ts=2 sts=2 sw=2
 
-function! airline#builder#new(active, highlighter)
-  let builder = {}
-  let builder._sections = []
-  let builder._active = a:active
-  let builder._highlighter = a:highlighter
+let s:prototype = {}
 
-  function! builder.split(gutter)
+function! s:prototype.split(gutter)
   call add(self._sections, ['|', a:gutter])
-  endfunction
+endfunction
 
-  function! builder.add_section(group, contents)
+function! s:prototype.add_section(group, contents)
   call add(self._sections, ['airline_'.a:group, a:contents])
-  endfunction
+endfunction
 
-  function! builder.add_raw(text)
+function! s:prototype.add_raw(text)
   call add(self._sections, ['_', a:text])
-  endfunction
+endfunction
 
-  function! builder._group(group)
+function! s:prototype._group(group)
   return self._active ? a:group : a:group.'_inactive'
-  endfunction
+endfunction
 
-  function! builder.build()
+function! s:prototype.build()
   let line = '%{airline#check_mode()}'
   let side = 0
   let prev_group = ''
@@ -53,10 +49,14 @@ function! airline#builder#new(active, highlighter)
     let prev_group = section[0]
   endfor
 
-    return {
-          \ 'statusline': line,
-          \ }
-  endfunction
+  return line
+endfunction
 
+function! airline#builder#new(active, highlighter)
+  let builder = copy(s:prototype)
+  let builder._sections = []
+  let builder._active = a:active
+  let builder._highlighter = a:highlighter
   return builder
 endfunction
+