[tools/perf] Fix JavaScript interpolation in action_runner calls

tools/perf/page_sets/system_health/media_stories.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from page_sets.system_health import platforms
 from page_sets.system_health import system_health_story
 
 from page_sets.login_helpers import google_login
 from page_sets.login_helpers import pandora_login
 
@@ skipping 28 matching lines @@
     action_runner.WaitForElement(element_function=element_function)
     action_runner.ClickElement(element_function=element_function)
 
   def _WaitForPlayTime(self, action_runner):
     action_runner.Wait(self.PLAY_DURATION)
     while self._GetTimeInSeconds(action_runner) < self.PLAY_DURATION:
       action_runner.Wait(
           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)
 
 
 ################################################################################
 # Audio stories.
 ################################################################################
 
 
 @benchmark.Disabled('all')  # crbug.com/649392
 class GooglePlayMusicDesktopStory(_MediaStory):
@@ skipping 46 matching lines @@
   PLAY_SELECTOR = None
   STOP_SELECTOR = '.pauseButton'
   TIME_SELECTOR = '.elapsedTime'
   SEARCH_SELECTOR = '.searchInput'
 
   def _Login(self, action_runner):
     pandora_login.LoginAccount(action_runner, 'pandora', self.credentials_path)
 
   def _NavigateToMedia(self, action_runner):
     pass  # Audio autoplays on Pandora, no need to search.