Reland of "Add StaleWhileRevalidateExperiment histograms."
Add histograms
PageLoad.Clients.StaleWhileRevalidateExperiment.Timing2.NavigationToLoadEventFired,
PageLoad.Clients.StaleWhileRevalidateExperiment.Timing2.NavigationToFirstLayout,
and
PageLoad.Clients.StaleWhileRevalidateExperiment.Timing2.NavigationToFirstTextPaint.
These behave the same as the base histograms, but they are only recorded
for a subset of domains which have render-blocking resources served with
the Cache-Control stale-while-revalidate directive.
These histograms permit us to measure the benefit in load time from the
implementation of the directive wihout noise from domains which don't
use it.
This CL was originally landed as
https://codereview.chromium.org/1433893002/ but reverted due to
accidentally introducing a static initialiser. This CL is identical to
the previous one except that it no longer aliases
base::StringPiece::npos to work around the static initialiser issue
http://crbug.com/561283.
TBR=eroman
BUG=348877
TEST=manual
Review URL: https://codereview.chromium.org/1479493002
Cr-Commit-Position: refs/heads/master@{#362491}
14 files changed
