Thanks Andreas, i will update with comment, however while running b2gperf today on master build after jan 30 , b2gperf failed even with this patch. Digging deeper the issue is In Bug 959186, platform is removed from testing/marionette/marionette-server.js

Running b2gperf on jan 30 master builds is throwing error keyError:'platform'

For backward compatibility we need platform in marionette server than only this patch will work across all build.