[tools/perf] Fix JavaScript interpolation in action_runner calls

tools/perf/page_sets/system_health/loading_stories.py

Index: tools/perf/page_sets/system_health/loading_stories.py
diff --git a/tools/perf/page_sets/system_health/loading_stories.py b/tools/perf/page_sets/system_health/loading_stories.py
index 2b0af06d974c17772a7682e534952b81a416138f..022d74f30093e3547e0cbc399a76e09e884c2a3c 100644
--- a/tools/perf/page_sets/system_health/loading_stories.py
+++ b/tools/perf/page_sets/system_health/loading_stories.py
@@ -187,9 +187,9 @@ class LoadWashingtonPostMobileStory(_LoadingStory):
     # window does not have a "Close" button, instead it has only a "Send link
     # to phone" button. So on tablets we run with the popup window open. The
     # popup is transparent, so this is mostly an aesthetical issue.
-    # TODO(catapult:#3028): Fix interpolation of JavaScript values.
     has_button = action_runner.EvaluateJavaScript(
-        '!!document.querySelector("%s")' % self._CLOSE_BUTTON_SELECTOR)
+        '!!document.querySelector({{ selector }})',
+        selector=self._CLOSE_BUTTON_SELECTOR)
     if has_button:
       action_runner.ClickElement(selector=self._CLOSE_BUTTON_SELECTOR)