[Telemetry] fix maps.py benchmark

The value of total time and render time from regular expression matching
are strings, not numbers. Do the conversion before adding to scalar
value.

BUG=None

Review URL: https://codereview.chromium.org/876063004

Cr-Commit-Position: refs/heads/master@{#315958}

tools/perf/benchmarks/maps.py

@@ -28,9 +28,9 @@ def ValidateAndMeasurePage(self, page, tab, results):
     total = re.search('total=([0-9]+)', test_results).group(1)
     render = re.search('render=([0-9.]+),([0-9.]+)', test_results).group(2)
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'total_time', 'ms', total))
+        results.current_page, 'total_time', 'ms', int(total)))
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'render_mean_time', 'ms', render))
+        results.current_page, 'render_mean_time', 'ms', float(render)))
 
 class MapsPage(page_module.Page):
   def __init__(self, page_set, base_dir):