Agree with the others. Have flown several mainland Chinese carriers on domestic routes (CA, MU, HU, FM, CZ, HO, KN) and no one's batted an eyelid at any of my carry on luggage or ever asked for it to be measured/weighed. Have never seen it happen to any other passenger at a Chinese airport either. There's always a first time for anything, but as long as it can fit in an overhead bin, you should be fine.