To future-proof the JSMarionette client it should have support for level 3 of the Marionette protocol outlined in bug 1211489. The changes required on the client side should this time be minimal as the command result data structures are not changing. However, the client should expect to receive "Response" messages and send "Command" messages as outlined in the message format description in bug 1211489.
Comment on attachment 8669730 [details] [review] [gaia] andreastt:bug_1211501 > mozilla-b2g:master LGTM though you seem to have a merge conflict now.
Expanded the commit message somewhat in https://treeherder.mozilla.org/#/jobs?repo=gaia&revision=8239a716a17223f04bc641eaedb7c417f9562cef and fixed the failing tests in https://treeherder.mozilla.org/#/jobs?repo=gaia&revision=78f56c00edeba90897f85a4ade06cb86026bcda2.