Because Breve triage is tomorrow: the CL is out for review. https://chromium-review.googlesource.com/c/chromium/src/+/1419101

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1a330a80fa001bb1b5dbfde56d6b3710216792ee

commit 1a330a80fa001bb1b5dbfde56d6b3710216792ee
Author: Sophie Chang <sophiechang@chromium.org>
Date: Fri Jan 18 18:41:06 2019

Add UMA for scheme-specific ParseStartToFirstContentfulPaint

Bug:  923091 
Change-Id: If6a8a3a00de6877e7b6c34c47fe1ac02b4b835b1
Reviewed-on: https://chromium-review.googlesource.com/c/1419101
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Sophie Chang <sophiechang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624209}
[modify] https://crrev.com/1a330a80fa001bb1b5dbfde56d6b3710216792ee/chrome/browser/page_load_metrics/observers/scheme_page_load_metrics_observer.cc
[modify] https://crrev.com/1a330a80fa001bb1b5dbfde56d6b3710216792ee/chrome/browser/page_load_metrics/observers/scheme_page_load_metrics_observer_unittest.cc
[modify] https://crrev.com/1a330a80fa001bb1b5dbfde56d6b3710216792ee/tools/metrics/histograms/histograms.xml