xtract PSS values of processes in a global memory dump. */
  function extractGlobalMemoryDumpUsedSizes(globalMemoryDump, addSize) {
    for (const [pid, pmd] of
      Object.entries(globalMemoryDump.processMemoryDumps)) {
      const mostRecentVmRegions = pmd.mostRecentVmRegions;
      if (mostRecentVmRegions === undefined) continue;
      addSize(pid, mostRecentVmRegions.byteStats.proportionalResident || 0,
          pmd.process.userFriendlyName);
    }
  }

  /** Extract sizes of root allocators in a proc