Add Wait* API to ActionRunner to wrap over WaitAction.

tools/perf/page_sets/media_cns_cases.py

Index: tools/perf/page_sets/media_cns_cases.py
diff --git a/tools/perf/page_sets/media_cns_cases.py b/tools/perf/page_sets/media_cns_cases.py
index 9824f5a55ed046c7e1094361d05bf649011b6839..2ba2451ea4340efc8f85a14855a791b62226be07 100644
--- a/tools/perf/page_sets/media_cns_cases.py
+++ b/tools/perf/page_sets/media_cns_cases.py
@@ -30,10 +30,7 @@ class BasicPlayPage(page_module.Page):
         'wait_for_ended': False
       }))
     # Wait for 1 second so that we know the play-head is at ~1s.
-    action_runner.RunAction(WaitAction(
-      {
-        'seconds': 1
-      }))
+    action_runner.Wait(1)
     # Seek to before the play-head location.
     action_runner.RunAction(SeekAction(
       {