Pakistan is China's closest ally. The only reason why China is not helping Pakistan even more is that it is not yet a superpower - by 2020 this will no longer be the case. By 2020 it should have the largest economy in the world and have 4-5 supercarriers battle groups in existence. Going foward China will close and surpass US in military strength as it's larger economy vis-a-vis the US comes into play. A reverse scenario of the US versus Russia during the cold war
To illustrate just how much China values Pakistan, you only need to look at their help in urgently deleivery 50 JF-17 Block 2's by June next year. China would not do this for any other country. China will make sure that Pakistan is sufficiently strong that India never considers any kind of military strike on Pakistan.
The historical links and Pakistan's strategic location give China very little choice but to back Pakistan up.
