metrics: Add experimental reported_by_page metric.

Add the experimental reported_by_page metric, which is a TBMv3 port of
the TBMv2 equivalent[1].

[1] https://github.com/catapult-project/catapult/blob/master/tracing/tracing/metrics/reported_by_page_metric.html

Bug: 174028247
Change-Id: I22e3f84fa997379d07f818834de9eb5845ebfcf5
diff --git a/BUILD b/BUILD
index 525a525..f84beb2 100644
--- a/BUILD
+++ b/BUILD
@@ -947,6 +947,7 @@
         "src/trace_processor/metrics/chrome/scroll_jank_cause_queuing_delay.sql",
         "src/trace_processor/metrics/chrome/test_chrome_metric.sql",
         "src/trace_processor/metrics/experimental/frame_times.sql",
+        "src/trace_processor/metrics/experimental/reported_by_page.sql",
         "src/trace_processor/metrics/trace_metadata.sql",
         "src/trace_processor/metrics/webview/webview_power_usage.sql",
     ],
@@ -2341,6 +2342,7 @@
     srcs = [
         "protos/perfetto/metrics/chrome/all_chrome_metrics.proto",
         "protos/perfetto/metrics/chrome/frame_times.proto",
+        "protos/perfetto/metrics/chrome/reported_by_page.proto",
         "protos/perfetto/metrics/chrome/test_chrome_metric.proto",
     ],
     visibility = [