[Seaside] updateRoot question

[Sean Allen]

is it possible for code that is executed during renderContentOn: to
add additional header info like updateRoot: does.
so basically, delay til renderContentOn decisions about what to add to
root and what not.

in psuedo something like:

renderContentOn: aCanvas

    aCanvas html: 'some html'.
    self renderMySpecialMethod.
    aCanvas html: 'some html'.

renderMySpecialMethod: aCanvas

   *magic to get html root*
   *do something with html root*
   aCanvas html: 'special html that needs something in the root to operate'.