added double checked lock to ensure thread safety on initialization.
added double checked lock to ensure thread safety on initialization.

codevlabs/Glimpse,dudzon/Glimpse,codevlabs/Glimpse,sorenhl/Glimpse,rho24/Glimpse,rho24/Glimpse,rho24/Glimpse,Glimpse/Glimpse,flcdrg/Glimpse,codevlabs/Glimpse,Glimpse/Glimpse,paynecrl97/Glimpse,gabrielweyer/Glimpse,sorenhl/Glimpse,elkingtonmcb/Glimpse,SusanaL/Glimpse,Glimpse/Glimpse,flcdrg/Glimpse,gabrielweyer/Glimpse,paynecrl97/Glimpse,SusanaL/Glimpse,dudzon/Glimpse,rho24/Glimpse,paynecrl97/Glimpse,paynecrl97/Glimpse,elkingtonmcb/Glimpse,dudzon/Glimpse,elkingtonmcb/Glimpse,sorenhl/Glimpse,flcdrg/Glimpse,SusanaL/Glimpse,gabrielweyer/Glimpse