[chromedriver] Make tabs visible when switching to windows/tabs.

chrome/test/chromedriver/session_commands.cc

Index: chrome/test/chromedriver/session_commands.cc
diff --git a/chrome/test/chromedriver/session_commands.cc b/chrome/test/chromedriver/session_commands.cc
index 1a39f53bc3a0574e07e8fb9e9ea019677c0ae3ee..96aee9de5a6a5401dba3826defb9f4109fff5970 100644
--- a/chrome/test/chromedriver/session_commands.cc
+++ b/chrome/test/chromedriver/session_commands.cc
@@ -435,6 +435,9 @@ Status ExecuteSwitchToWindow(Session* session,
       return status;
   }
 
+  status = session->chrome->ActivateWebView(web_view_id);
+  if (status.IsError())
+    return status;
   session->window = web_view_id;
   session->SwitchToTopFrame();
   session->mouse_position = WebPoint(0, 0);