[Telemetry] Fix JavaScript interpolation in telemetry actions

telemetry/telemetry/internal/actions/seek.py

Index: telemetry/telemetry/internal/actions/seek.py
diff --git a/telemetry/telemetry/internal/actions/seek.py b/telemetry/telemetry/internal/actions/seek.py
index df9ead4489cb12143eeb86cd538933c028038d60..040cee89f518c37860d29cda6f1a24463ca96baf 100644
--- a/telemetry/telemetry/internal/actions/seek.py
+++ b/telemetry/telemetry/internal/actions/seek.py
@@ -21,6 +21,7 @@ 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 SeekAction(media_action.MediaAction):
@@ -39,11 +40,17 @@ class SeekAction(media_action.MediaAction):
     utils.InjectJavaScript(tab, 'seek.js')
 
   def RunAction(self, tab):
+    # TODO(catapult:#3028): Render in JavaScript method when supported by API.
+    code = js_template.Render(
+        'window.__seekMedia('
+            '{{ selector }}, {{ seconds }}, {{ log_time }}, {{ label}});',
+        selector=self._selector,
+        seconds=str(self._seconds),  #  TODO: Is string convertion intended?
+        log_time=self._log_time,
+        label=self._label)
     try:
       # TODO(catapult:#3028): Fix interpolation of JavaScript values.
-      tab.ExecuteJavaScript(
-          'window.__seekMedia("%s", "%s", %i, "%s");' %
-          (self._selector, self._seconds, self._log_time, self._label))
+      tab.ExecuteJavaScript(code)
       if self._timeout_in_seconds > 0:
         self.WaitForEvent(tab, self._selector, 'seeked',
                           self._timeout_in_seconds)