Add mapped_file metric

[stevenjm]

This is a simple fix for #2016.

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[stevenjm]

I signed it!

[dashpole]

/ok-to-test

[gwkunze]

I signed it!

Corporate CLA has been signed, I checked the email address for the commit and it matches as far as I can tell.

[stevenjm]

cla update

[stevenjm]

@dashpole Both the committer and the PR author are covered by the same signed corporate CLA, but the automation doesn't seem to be recognising that. Is there anything left for us to do?

[dashpole]

I can check to see if the corporate CLA has been processed. Can you ping me the name of the corporation on slack (username is dashpole), or email it to me?

[stevenjm]

Closing this so the commit author can open one and hopefully get the CLA check to pass.

[stevenjm]

Replacement PR: #2034