Add offline URL param
Add offline URL param

Simplifies rapid testing of offline playback.

Change-Id: I529c6e0e50ea723263cfa00798742055761c7f5b

blinkbox/shaka-player,ustudio/shaka-player,Afrostream/shaka-player,shaka-project/shaka-player,brightcove/shaka-player,treejames/shaka-player,TheModMaker/shaka-player,tvoli/shaka-player,indiereign/shaka-player,TobbeEdgeware/shaka-player,baconz/shaka-player,vimond/shaka-player,treejames/shaka-player,baconz/shaka-player,indiereign/shaka-player,blinkbox/shaka-player,baconz/shaka-player,vimond/shaka-player,Ross-cz/shaka-player,sanbornhnewyyz/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,TobbeEdgeware/shaka-player,priyajeet/shaka-player,vimond/shaka-player,priyajeet/shaka-player,priyajeet/shaka-player,Afrostream/shaka-player,Afrostream/shaka-player,cmgrecu/shaka-player,shaka-project/shaka-player,brightcove/shaka-player,cmgrecu/shaka-player,Afrostream/shaka-player,ustudio/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,TobbeEdgeware/shaka-player,ustudio/shaka-player,russitto/shaka-player,ustudio/shaka-player,TheModMaker/shaka-player,sanbornhnewyyz/shaka-player,blinkbox/shaka-player,indiereign/shaka-player,priyajeet/shaka-player,samdutton/shaka-player,brightcove/shaka-player,russitto/shaka-player,samdutton/shaka-player,Ross-cz/shaka-player,sanbornhnewyyz/shaka-player,blinkbox/shaka-player,sanbornhnewyyz/shaka-player,treejames/shaka-player,samdutton/shaka-player,treejames/shaka-player,TheModMaker/shaka-player,russitto/shaka-player,TheModMaker/shaka-player,cmgrecu/shaka-player,tvoli/shaka-player,Ross-cz/shaka-player,samdutton/shaka-player