[tbmv3] Add TBMv3 UMA metrics to rendering benchmark

This change adds new events with disabled-by-default-histogram_samples
category to trace.
No new metrics will be calculated unless --experimental-tbmv3-metrics
flag is supplied.
For the effect of enabling disabled-by-default-histogram_samples
category, see https://crrev.com/c/2363747

TBMv3 UMA metrics: tools/perf/core/tbmv3/metrics/uma_metrics.proto

Pinpoint results (rendering benchmark):
 - lunux-perf:
 - - https://pinpoint-dot-chromeperf.appspot.com/job/17ff0df5920000
 - - (rerun) https://pinpoint-dot-chromeperf.appspot.com/job/133badbd920000
 - - (tbmv3) https://pinpoint-dot-chromeperf.appspot.com/job/1649f905920000
 - win-10_laptop_low_end-perf:
 - - https://pinpoint-dot-chromeperf.appspot.com/job/17c055ed920000
 - - (tbmv3) https://pinpoint-dot-chromeperf.appspot.com/job/150ecc35920000
 - android-pixel2-perf:
 - - https://pinpoint-dot-chromeperf.appspot.com/job/100100dd920000
 - - (tbmv3) https://pinpoint-dot-chromeperf.appspot.com/job/131d55d5920000
 - android-go-perf:
 - - (tbmv3) https://pinpoint-dot-chromeperf.appspot.com/job/17354c30520000

Bug: 1119834
Change-Id: I71379f16430674999bd3615722a1a446b1714f6e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2388201Reviewed-by: Deep Roy <dproy@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Julia Semavina <nuwanda@google.com>
Cr-Commit-Position: refs/heads/master@{#807982}

tools/perf/benchmarks/rendering.py

@@ -70,10 +70,19 @@ class _RenderingBenchmark(perf_benchmark.PerfBenchmark):
     # Supplement the base trace categories with "gpu.memory" which records
     # timings associated with memory ablation experiments.
     category_filter.AddFilterString('gpu.memory')
+    category_filter.AddDisabledByDefault(
+        'disabled-by-default-histogram_samples')
     options = timeline_based_measurement.Options(category_filter)
     options.config.chrome_trace_config.EnableUMAHistograms(
         *RENDERING_BENCHMARK_UMA)
-    options.SetTimelineBasedMetrics(['renderingMetric', 'umaMetric', 'memoryAblationMetric'])
+    options.SetTimelineBasedMetrics([
+        'renderingMetric',
+        'umaMetric',
+        'memoryAblationMetric',
+        # Unless --experimentatil-tbmv3-metric flag is used, the following tbmv3
+        # metrics do nothing.
+        'tbmv3:uma_metrics'
+    ])
     return options