It turns out that the API would be easier for devtools API users if it were this way. We would need to restructure the event data to something like { // Whether this is an incremental slice, or not. isIncrementalSlice: true|false, // This would just be the major GC number, used to identify // which slices are related to each other. incrementalGCCycle: Number, // If nonincremental, string saying why. nonincrementalReason: null|string, // Short string describing why we are GCing at all. reason: string, // Timestamps for the start and end of this slice/collection. startTimestamp: timestamp, endTimestamp: timestamp }