If developer mode / persistent overlay is enabled, do not provide
a dialog for updating images (images can still be updated through
other means, but we take this opportunity to tell user that he/she
is in developer mode and should not expect to be able to update
the system in the normal way).
client/restricted-packages/google-chrome: Configure chromium to use chrome's
flash library when it is installed.
client/restricted-packages/google-chrome: Use direct download url
restricted-packages: Add gpg support for file integrity checking
client/restricted-packages/dropbox: Use a temp file for download