As a result of the removal of the Experience Sampling extension API ( issue 810420 ), the ChromeMetricsHelper class [1] seems a bit superfluous now that it doesn't help handle experience sampling events. The only remaining specialization is for captive portal so we may be able to move that logic back into the captive portal interstitials and remove this class. However, this class is currently used by a lot of the interstitials, so we'll need to investigate further. Likely we can refactor the interstitials and get rid of ChromeMetricsHelper.

[1] https://cs.chromium.org/chromium/src/chrome/browser/interstitials/chrome_metrics_helper.h?q=ChromeMetricsHelper&sq=package:chromium&dr=CSs&l=31