Expose Context#PAC_PROXY_SERVICE as module lib API

(cherry-picked from ag/14097767)
Bug: 183938000
Test: make update-api
Merged-In: I4341e177b61df0311f0a3234f8814a0ae2cf9a1b
Change-Id: I4341e177b61df0311f0a3234f8814a0ae2cf9a1b
2 files changed