asset: add missing license header
asset: add missing license header

Change-Id: Ife81591606a2fadcc216eae0ea17d772b3757cf7
Reviewed-on: https://go-review.googlesource.com/11736
Reviewed-by: Hyang-Ah Hana Kim <d7e82c3c07f92613bcbf9a1e88f6b96c13caa3b0@gmail.com>

xing/gomobile,swisspol/mobile,xing/gomobile,lonphy23t/mobile,DanielWorld/mobile,cainiaocome/mobile,b54898533/mobile,goldcaddy77/mobile,freeman0211/mobile,freeman0211/mobile,ichu501/mobile,MaxCy330/mobile,xing/gomobile,ppamorim/mobile,samanalysis/mobile,tempbottle/mobile,samanalysis/mobile,golang/mobile,steeve/mobile,samanalysis/mobile,zach-klippenstein/mobile,MaxCy330/mobile,MaxCy330/mobile,ichu501/mobile,cainiaocome/mobile,swisspol/mobile,xing/gomobile,golang/mobile,MaxCy330/mobile,zach-klippenstein/mobile,0x90sled/mobile,lonphy23t/mobile,freeman0211/mobile,b54898533/mobile,lonphy23t/mobile,swisspol/mobile,samanalysis/mobile,qskycolor/mobile,goldcaddy77/mobile,0x90sled/mobile,ppamorim/mobile,lonphy23t/mobile,tempbottle/mobile,ichu501/mobile,steeve/mobile,golang/mobile,goldcaddy77/mobile,ichu501/mobile,ppamorim/mobile,lonphy23t/mobile,0x90sled/mobile,swisspol/mobile,samanalysis/mobile,xing/gomobile,0x90sled/mobile,DanielWorld/mobile,0x90sled/mobile,ppamorim/mobile,tempbottle/mobile,tempbottle/mobile,goldcaddy77/mobile,cainiaocome/mobile,freeman0211/mobile,ichu501/mobile,qskycolor/mobile,MaxCy330/mobile,swisspol/mobile,cainiaocome/mobile,DanielWorld/mobile,steeve/mobile,zach-klippenstein/mobile,steeve/mobile,tempbottle/mobile,golang/mobile,zach-klippenstein/mobile,cainiaocome/mobile,b54898533/mobile,qskycolor/mobile,b54898533/mobile,ppamorim/mobile,DanielWorld/mobile,b54898533/mobile,goldcaddy77/mobile,qskycolor/mobile