The log output is

I/Gecko   ( 5547): 1386274915225        Marionette      DEBUG Got request: executeWithCallback, data: {"name":"executeAsyncScript","parameters":{"script":"window.wrappedJSObject.PerformanceHelperAtom.waitForEvent(\"startup-path-done\");","args":[]},"to":"0","session":"6-b2g"}, id: {59f56288-3971-443c-98c2-1d676d18045a}