asset: hoist global variable to Go and make C function static
asset: hoist global variable to Go and make C function static

Change-Id: I19d933bb49eba462371451ac3b258744c69b0aad
Reviewed-on: https://go-review.googlesource.com/124916
Reviewed-by: Hyang-Ah Hana Kim <d7e82c3c07f92613bcbf9a1e88f6b96c13caa3b0@gmail.com>

golang/mobile,golang/mobile,golang/mobile,golang/mobile