START
   |
   V
 Is there a Content-Type and is the UA going to obey it blindly?
   |                   |
   | YES               | NO
   |                   V                                                          YES
   |                 Is there a type="" attribute whose value is a plugin type? ---------.
   |                   |                                                                 V
   |                   | NO                                                    YES ,--->-+
   |                   V                        NO                                 |     |
   |                 Is there a Content type? ----->-+-> Is there a type="" attribute?   |
   |                   |                             ^                             |     |
   |                   | YES                         `------------------------.    | NO  |
   V            NO     V                                                      |    |     |
   +-<-------------- Is it text/plain or application/octet-stream?            |    `----)|(-----> Is there an extension?
   |                   |                                     |                |          |         |                |
   |                   | text/plain                          | octet-stream   |          |         | YES            | NO
   |                   V                                     V                |          |         V                V
   |                 Does the page sniff as binary?         Set S flag -------'          |        Use              Sniff
   |                   |              |                                                  |        extension         |
   |                   | NO           | YES                                              |         |                |
   |                   V        NO    V                             YES                  V         |                |
   |                   +-<--------- Is there a type="" attribute? ------> Set S flag -->-+         |                |
   |                   |                                                                 |         |                |
   |                   |                                                                 V         |                |
   V                   V                                                                Use        |                |
  Use                 Use                                                               type=""    |                |
  Content-Type        text/plain                                                        attribute  |                |
   |                   |                                                                 |         |                |
   |                   V                                                                 V         V                |
   `----------------->-+--------------------------------------------------------------> END <------+-<--------------'

           S flag means that if the resulting type is an XML type, or
           is a type that doesn't start with "image/", then fallback
           is used instead. (i.e. if the S flag is set, only plugins
           and unscripted bitmap images are supported.)