Before revision: During the transition of the input line from one voltage level to the other, there is a period of time when both the PMOS and the NMOS transistors are on, thus creating a path from VDD to ground.
After revision: During the transition of the output line (of a CMOS gate) from one voltage level to the other, there is a period of time when both the PMOS and the NMOS transistors are on, thus creating a path from VDD to ground.