text: #include "association_transformer.h"
  Extremely simple slot which just sets an association in a std::map when it is Render()ed. It associates the key (input URL) with this slot's resource URL (the output URL). Can be used to set AssociationTransformer::map() so that AssocitationTransformer::Transform() will rewrite the rendered URLs.
  Update the URL in the slot target without touching the resource. This is intended for when we're inlining things as data: URLs and also for placing the rewritten version of the URL in the slot. The method returns true if it successfully updates the slot target. Resources that are not explicitly authorized will get rejected at this point. Note that if you call this you should also call set_disable_rendering(true), or otherwise the result will be overwritten. Does not alter the URL in any way. Not supported on all slot types — presently only slots representing things within CSS and HTML have this operation (others will DCHECK-fail). Must be called from within a context's Render() method.
  We should never try to render unauthorized resource URLs as is.
  Reimplemented from net_instaweb::ResourceSlot.
  Returns a human-readable description of where this slot occurs, for use in log messages.
  Implements net_instaweb::ResourceSlot.
  All Render() calls are from the same thread, so this doesn't need to be thread-safe.
  We should never try to render unauthorized resource URLs as is.
  Implements net_instaweb::ResourceSlot.