Image measurement and fragment merging decoded every /Contents entry
and every form occurrence with a fresh 1 GiB allowance, so repeated
references to one compressed stream multiplied memory. Both charge a
per-page DecodeBudget. A page whose content does not decode within it
is left unmerged, and its images are not resampled, since a use may be
missed; fragment merging no longer rewrites a page from content it
could not fully decode.