A different point if view by Raffaello Pantucci, highlighting:
It is, however, increasingly clear that there is a high level of concern in China about Pakistan. In Xinjiang in particular they seem to have lost patience at Pakistani capacity to contain Uighur extremists travelling to train in Pakistan and then coming back.
It which ends with:
Beijing may be Pakistan’s best friend, but even best friends can eventually lose their patience with each other.
Link:http://raffaellopantucci.com/2012/06...akistan-china/

Given the current state of Pakistan's relations with the USA primarily even a cooling of Sino-Pakistani relations could unsettle strategic thinking, after all as a nation Pakistan needs steady friends and money.