Ok, I have removed the ShareContainer from LyXFont and use it on
LyXParagraph::FontTable::font instead.
I am not sure if ShareContainer is optimal yet, probably not.
Last test said:
time ./src/lyx -x lyx-quit ../../local/lyxdoc/UserGuide.l
yx
About to handle -x 'lyx-quit'
real 0m7.264s
user 0m4.510s
sys 0m0.070s
Lgb
one more