RenderThreadImpl::HistogramCustomizer::HistogramCustomizer() {
  custom_histograms_.insert("V8.MemoryExternalFragmentationTotal");
  custom_histograms_.insert("V8.MemoryHeapSampleTotalCommitted");
  custom_histograms_.insert("V8.MemoryHeapSampleTotalUsed");
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.