How to set alias in gnome?

[Miao Jiang <jiangfriend gmail com>]

I want to set an alias '
alias chromium-browser='chromium-browser 
--disk-cache-dir=/dev/shm/chromium --disk-cache-size=512000000'
to speed up chromium

but I tried add the alias line to
/etc/profile
/etc/X11/Xsession.d/55gnome-session_gnomerc
~/.bashrc
~/.gnomerc
~/.xinitrc

The alias doesn't work for running through 'Alt+F2' or Launcher

Thanks
Miao