[tools/perf] Fix JavaScript interpolation in action_runner calls

tools/perf/page_sets/system_health/media_stories.py

Index: tools/perf/page_sets/system_health/media_stories.py
diff --git a/tools/perf/page_sets/system_health/media_stories.py b/tools/perf/page_sets/system_health/media_stories.py
index 6a8501f92ba84dd18eb3eb8be153d992e39d2fe3..f195bf62f8c0951280dc8bda0ea7cbee4059bc16 100644
--- a/tools/perf/page_sets/system_health/media_stories.py
+++ b/tools/perf/page_sets/system_health/media_stories.py
@@ -46,10 +46,9 @@ class _MediaStory(system_health_story.SystemHealthStory):
           self.PLAY_DURATION - self._GetTimeInSeconds(action_runner))
 
   def _GetTimeInSeconds(self, action_runner):
-    # TODO(catapult:#3028): Fix interpolation of JavaScript values.
-    time_func = (
-        'document.querySelector("%s").textContent' % self.TIME_SELECTOR)
-    minutes, seconds = action_runner.EvaluateJavaScript(time_func).split(':')
+    minutes, seconds = action_runner.EvaluateJavaScript(
+        'document.querySelector({{ selector }}).textContent',
+        selector=self.TIME_SELECTOR).split(':')
     return int(minutes * 60 + seconds)