This friendly act on China's part, could really make a huge difference on the ground within the next few years. Sri Lanka already has a battle-hardened army. And China's military&strategic training institutes are likely to base their material and curriculum to counter the latest strategies and tactics deployed by the west in warfare.
So if Sri Lanka's battle-hardened army gets trained in modern tactics and strategic warfare, it's no surprise that Indians would make alot of noise about this development. They like their neighbors to be comfortably under India's thumb, at their mercy. Pakistan's founding father Quaid-e-Azam said "Weakness invites aggression". With neighbors like India, this is a wonderful move by Sri Lanka. In the long run, they should be a small but surprisingly effective force like Switzerland, to convince any aggressor that the cost of aggression against Sri Lanka would be enormous.