The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4244d4e4d0a4dc0e6fd0eea57801dfbf41401600

commit 4244d4e4d0a4dc0e6fd0eea57801dfbf41401600
Author: bmcquade <bmcquade@chromium.org>
Date: Wed Apr 05 23:52:46 2017

Add additional metrics for subresource filtering.

This change adds the following:
* parse blocking script breakouts, so we can better understand differences in
  improvements to FCP/FMP due to doc.write blocking vs general subresource
  filtering
* foreground duration, so we can understand time on page when subresource
  filtering is active
* byte and resource counts for pages where media was played

BUG= 708162 

Review-Url: https://codereview.chromium.org/2795453003
Cr-Commit-Position: refs/heads/master@{#462278}

[modify] https://crrev.com/4244d4e4d0a4dc0e6fd0eea57801dfbf41401600/chrome/browser/page_load_metrics/observers/subresource_filter_metrics_observer.cc
[modify] https://crrev.com/4244d4e4d0a4dc0e6fd0eea57801dfbf41401600/chrome/browser/page_load_metrics/observers/subresource_filter_metrics_observer.h
[modify] https://crrev.com/4244d4e4d0a4dc0e6fd0eea57801dfbf41401600/chrome/browser/page_load_metrics/observers/subresource_filter_metrics_observer_unittest.cc
[modify] https://crrev.com/4244d4e4d0a4dc0e6fd0eea57801dfbf41401600/tools/metrics/histograms/histograms.xml