The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f9bf372ebfcea5043ba08a15320e8ddace508f19

commit f9bf372ebfcea5043ba08a15320e8ddace508f19
Author: bmcquade <bmcquade@chromium.org>
Date: Tue Feb 14 00:20:56 2017

Add subresource filter page load metrics observer

SubresourceFilterMetricsObserver tracks key page load
performance metrics, as well as bytes loaded per page,
for page loads where at least one subresource was filtered.

BUG= 690161 

Review-Url: https://codereview.chromium.org/2684153003
Cr-Commit-Position: refs/heads/master@{#450167}

[modify] https://crrev.com/f9bf372ebfcea5043ba08a15320e8ddace508f19/chrome/browser/BUILD.gn
[add] https://crrev.com/f9bf372ebfcea5043ba08a15320e8ddace508f19/chrome/browser/page_load_metrics/observers/subresource_filter_metrics_observer.cc
[add] https://crrev.com/f9bf372ebfcea5043ba08a15320e8ddace508f19/chrome/browser/page_load_metrics/observers/subresource_filter_metrics_observer.h
[add] https://crrev.com/f9bf372ebfcea5043ba08a15320e8ddace508f19/chrome/browser/page_load_metrics/observers/subresource_filter_metrics_observer_unittest.cc
[modify] https://crrev.com/f9bf372ebfcea5043ba08a15320e8ddace508f19/chrome/browser/page_load_metrics/page_load_metrics_initialize.cc
[modify] https://crrev.com/f9bf372ebfcea5043ba08a15320e8ddace508f19/chrome/browser/page_load_metrics/page_load_tracker.cc
[modify] https://crrev.com/f9bf372ebfcea5043ba08a15320e8ddace508f19/chrome/browser/subresource_filter/subresource_filter_browsertest.cc
[modify] https://crrev.com/f9bf372ebfcea5043ba08a15320e8ddace508f19/chrome/test/BUILD.gn
[modify] https://crrev.com/f9bf372ebfcea5043ba08a15320e8ddace508f19/tools/metrics/histograms/histograms.xml