There is no dialog latency data since yesterday, it is caused by...

There is no dialog latency data since yesterday, it is caused by crrev.com/1907073002, the action to open/close dialog was deleted by mistake.

This change just adds the action to open/close dialog back.

BUG=

Review URL: https://codereview.chromium.org/1919293002

Cr-Commit-Position: refs/heads/master@{#389834}

chrome/test/media_router/telemetry/benchmarks/pagesets/media_router_perf_pages.py

@@ -33,7 +33,16 @@ class CastDialogPage(media_router_page.CastPage):
         shared_page_state_class=shared_page_state_class)
 
   def RunPageInteractions(self, action_runner):
-     pass
+    # Wait for 5s after Chrome is opened in order to get consistent results.
+    action_runner.Wait(5)
+    with action_runner.CreateInteraction('OpenDialog'):
+      # Open dialog
+      action_runner.TapElement(selector='#start_session_button')
+      action_runner.Wait(5)
+      # Close media router dialog
+      for tab in action_runner.tab.browser.tabs:
+        if tab.url == 'chrome://media-router/':
+          self.CloseDialog(tab)
 
 
 class CastIdlePage(CastDialogPage):