mdw and bengr,

 crbug.com/689659  (marked as fixed) tracks the new HTTP histograms. There are histograms for original length and content length, but no histograms for the difference between content length and original (this can be added if it is necessary), feel free to re-open the bug. It might be good to read the last few comments in the bug explaining why certain histograms are empty.

My recommendation for histograms moving forward is to keep the following histograms:
Net.HttpContentLengthV2* (the new histograms)
Net.HttpContentLengthCacheable
Net.HttpContentLengthCacheable24Hours
Net.HttpContentLengthCacheable4Hours

and to remove the other content length histograms:
Net.Daily[Original]ContentLength*  (e.g. Net.DailyContentLength_DataReductionProxyEnabled; there are about 40 of these, I can provide an exhaustive list if needed)

Net.HttpContentLengthDifferenceWithValidOCL.LoFiOn
Net.HttpOriginalContentLengthWithValidOCL
Net.HttpOriginalContentLengthWithValidOCL.LoFiOn
Net.HttpContentLength
Net.HttpContentLengthDifference
Net.HttpContentLengthDifferenceWithValidOCL

Let me know if I should proceed with removing these, or if various metrics reports/dashboards need to be updated first.

Refreshed during triage.

The plan sgtm, except I don't know why we have the *Cacheable* histograms. Verify with mdw@ as he's a significant consumer before proceeding.

SGTM - seems fine to me to remove the old ones per Ryan's recommendation in #3.

(BTW, Ben -- it would have been faster for you to CC me on the bug as I am generally not that good at noticing references to my LDAP in random bug comments :-)

Done