Use pregenerate_update flag for devserver.
Use pregenerate_update flag for devserver.

Change-Id: I4a6fc66db7b336ae07bdfa837dd5e0d806880e52

BUG=8255
TEST=Ran it with devserver with option.

Review URL: http://codereview.chromium.org/4169006

endocode/scripts,coreos/scripts,bcwaldon/coreos-scripts,BugRoger/scripts,andrejro/coreos--scripts,vmware/coreos-scripts,fivethreeo/scripts,nicescale/scripts,mjg59/scripts,marineam/coreos-scripts,sigma/coreos-scripts,zhang0137/scripts,andrejro/coreos--scripts,crawford/scripts,endocode/scripts,fivethreeo/scripts,mjg59/scripts,mischief/scripts,BugRoger/scripts,nicescale/scripts,trnubo/scripts,glevand/coreos--scripts,endocode/scripts,gtank/scripts,zhang0137/scripts,trnubo/scripts,gtank/scripts,zhang0137/scripts,sigma/coreos-scripts,bcwaldon/coreos-scripts,marineam/coreos-scripts,crawford/scripts,vmware/coreos-scripts,mischief/scripts,bcwaldon/coreos-scripts,marineam/coreos-scripts,BugRoger/scripts,smilart/scripts,vmware/coreos-scripts,andrejro/coreos--scripts,smilart/scripts,mischief/scripts,glevand/coreos--scripts,fivethreeo/scripts,trnubo/scripts,mjg59/scripts,coreos/scripts,sigma/coreos-scripts,smilart/scripts,nicescale/scripts,crawford/scripts,gtank/scripts