Include more metrics in default ad_tagging.cluster_telemetry benchmark

Specifically we add the following high-level metrics: PageLoad.Clients.
Ads.AllPages.PercentNetworkBytes (percentage of bytes that are ads) and
PageLoad.Clients.Ads.AllPages.NonAdNetworkBytes (total non-ad bytes).

These metrics will aid tracking the accuracy of AdTagging over time and
also aid in understanding the impact of any proposed cl on AdTagging.

Bug: 1090494
Change-Id: Ie912cec6782a8aa883bc3a38db7fa4e48c0067b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2226064
Commit-Queue: Alex Turner <alexmt@chromium.org>
Reviewed-by: John Delaney <johnidel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#777466}

tools/perf/contrib/cluster_telemetry/ad_tagging_ct.py

@@ -72,6 +72,8 @@ class AdTaggingClusterTelemetry(perf_benchmark.PerfBenchmark):
         'Ads.ResourceUsage.Size.Network.Mainframe.VanillaResource',
         'Ads.ResourceUsage.Size.Network.Subframe.AdResource',
         'Ads.ResourceUsage.Size.Network.Subframe.VanillaResource',
+        'PageLoad.Clients.Ads.AllPages.NonAdNetworkBytes',
+        'PageLoad.Clients.Ads.AllPages.PercentNetworkBytesAds',
         'PageLoad.Clients.Ads.Cpu.AdFrames.Aggregate.TotalUsage',
         'PageLoad.Clients.Ads.Cpu.FullPage.TotalUsage',
         'PageLoad.Clients.Ads.FrameCounts.AdFrames.Total',