[Telemetry] Fix JavaScript interpolation in telemetry actions

telemetry/telemetry/internal/actions/play.py

Index: telemetry/telemetry/internal/actions/play.py
diff --git a/telemetry/telemetry/internal/actions/play.py b/telemetry/telemetry/internal/actions/play.py
index dc031727fa56fb9c49175556330629065a37ae4e..23b3b97394bdb11a763240ea3b126806706d856f 100644
--- a/telemetry/telemetry/internal/actions/play.py
+++ b/telemetry/telemetry/internal/actions/play.py
@@ -17,6 +17,7 @@ from telemetry.core import exceptions
 from telemetry.internal.actions import media_action
 from telemetry.internal.actions import page_action
 from telemetry.internal.actions import utils
+from telemetry.util import js_template
 
 
 class PlayAction(media_action.MediaAction):
@@ -34,9 +35,11 @@ class PlayAction(media_action.MediaAction):
     utils.InjectJavaScript(tab, 'play.js')
 
   def RunAction(self, tab):
+    # TODO(catapult:#3028): Render in JavaScript method when supported by API.
+    code = js_template.Render(
+        'window.__playMedia({{ selector }});', selector=self._selector)
     try:
-      # TODO(catapult:#3028): Fix interpolation of JavaScript values.
-      tab.ExecuteJavaScript('window.__playMedia("%s");' % self._selector)
+      tab.ExecuteJavaScript(code)
       # Check if we need to wait for 'playing' event to fire.
       if self._playing_event_timeout_in_seconds > 0:
         self.WaitForEvent(tab, self._selector, 'playing',