UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/65.0.3325.181 Chrome/65.0.3325.181 Safari/537.36

Steps to reproduce the problem:
The Chromium dev tools protocol supports getting histograms with
|getHistogram(s)|:
https://chromedevtools.github.io/devtools-protocol/tot/Browser/#method-getHistograms.
This returns the cumulative counts across the lifetime of the histograms.  It
would be good to have the option to request just the _delta_ of counts since the
previous call to getHistogram(s).  This would support the use case, particularly
in headless, where one wishes to periodically report metric data back to a
metrics collection server, while avoiding double-counting observations.

It looks like Chromium already has most of the code in place to support this use
case, as periodic reporting of deltas is how Google Chrome handles histograms.
As such, I believe the code additions/modifications would be fairly
straight-forward.  For example, instead of using
HistogramBase::SnapshotSamples() as is done here:
https://cs.chromium.org/chromium/src/content/browser/devtools/protocol/browser_handler.cc?l=53&rcl=2a90c8832699db230eb17897101296527c289605.
Use HistogramBase::SnapshotDelta().

What is the expected behavior?
.

What went wrong?
.

Did this work before? N/A 

Chrome version: 65.0.3325.181  Channel: n/a
OS Version: 
Flash Version: