The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f564b5a80caa74b761951b2d9a6772eb80c473b0

commit f564b5a80caa74b761951b2d9a6772eb80c473b0
Author: mattcary <mattcary@chromium.org>
Date: Mon Jan 02 10:59:32 2017

[Prerender] Add first contentful paint histograms

Uses perceived FCP measured from prerender swap time when appropriate.
Changes no state prefetch to use the same FCP histogram for easier
experimentation. If a page is hidden during prerendering, the paint
may be delayed in an unpredictable manner; therefore the histograms are
split between hidden and visible.

BUG= 657762 , 667243 

Review-Url: https://codereview.chromium.org/2423383002
Cr-Commit-Position: refs/heads/master@{#441056}

[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/BUILD.gn
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/page_load_metrics/metrics_web_contents_observer_unittest.cc
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.cc
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.h
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/page_load_metrics/observers/page_load_metrics_observer_test_harness.cc
[add] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/page_load_metrics/observers/prerender_page_load_metrics_observer.cc
[add] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/page_load_metrics/observers/prerender_page_load_metrics_observer.h
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/page_load_metrics/page_load_metrics_embedder_interface.h
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/page_load_metrics/page_load_tracker.cc
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/prerender/prerender_browsertest.cc
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/prerender/prerender_histograms.cc
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/prerender/prerender_histograms.h
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/prerender/prerender_manager.cc
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/prerender/prerender_manager.h
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/prerender/prerender_tab_helper.cc
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/prerender/prerender_tab_helper.h
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/prerender/prerender_test_utils.cc
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/browser/prerender/prerender_test_utils.h
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/test/BUILD.gn
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/chrome/test/data/prerender/prerender_page.html
[modify] https://crrev.com/f564b5a80caa74b761951b2d9a6772eb80c473b0/tools/metrics/histograms/histograms.xml