Benchpress does not report script time or gc in the upcoming Chrome 45. Changes to their tracing events:
script time:
Is reported with category devtools.timeline,v8 and name FunctionCall (used to be other category).
gc time:
Is reported via category devtools.timeline,v8 and name MinorGC / MajorGC (used to be other category and different name). Also, the name majorGC is not reported for category v8 any more.