chromium/tools/metrics/histograms/test_data/tokens/histograms.xml

<histogram-configuration>

<histograms>

<histogram name="Test.{TestToken3}.Histogram.{TestToken}.{TestToken2}"
    units="microseconds" expires_after="M85">
  <owner>[email protected]</owner>
  <summary>Summary</summary>
  <token key="TestToken" variants="TestToken"/>
  <token key="TestToken2">
    <variant name="TestName" summary="summary"/>
  </token>
  <token key="TestToken3" variants="TestToken3"/>
</histogram>

</histograms>

</histogram-configuration>