[trace processor] Add WebView power usage metric

This change adds a set of queries that calculate WebView power usage
based on the proxy power metric. A follow-up CL will remove
webview_cpu_usage.sql when downstream clients are updated to use
webview_power_usage.sql.

Bug: 158665114
Change-Id: Id7abfc7afd8106f8679b780240c7ce703bd44a10
diff --git a/Android.bp b/Android.bp
index 6d3a72d..c4bf062 100644
--- a/Android.bp
+++ b/Android.bp
@@ -57,6 +57,7 @@
     "src/trace_processor/metrics/chrome/chrome_processes.sql",
     "src/trace_processor/metrics/trace_metadata.sql",
     "src/trace_processor/metrics/webview/webview_cpu_usage.sql",
+    "src/trace_processor/metrics/webview/webview_power_usage.sql",
   ],
   cmd: "$(location tools/gen_merged_sql_metrics.py) --cpp_out=$(out) $(in)",
   out: [