Retry shutdown

Signed-off-by: Euclid Ye <yezhizhenjiakang@gmail.com>

Author: yezhizhen

tools/wptrunner/wptrunner/browsers/servodriver.py

@@ -144,17 +144,15 @@ def is_alive(self):
         return True
 
     def stop(self, force=False):
-        if self.is_alive():
-            self.logger.info("Shutting down gracefully by extension command")
-            conn = HTTPConnection(self.host, self.port)
+        conn = HTTPConnection(self.host, self.port)
+        while self.is_alive():
+            self.logger.info("Trying to shut down gracefully by extension command")
+            
             conn.request("DELETE", "/session/dummy-session-id/servo/shutdown")
             res = conn.getresponse()
             self.logger.info(f"Got response status for shutdown command: {res.status}")
-            # 0.05 is a heuristic value manually tested, after which servo always shutted down.
-            time.sleep(0.05)
-            while self.is_alive():
-                self.logger.info("Still alive. Retry in 0.05 second")
-                time.sleep(0.05)
+            
+            time.sleep(0.1)
 
     def find_wpt_prefs(self, logger):
         default_path = os.path.join("resources", "wpt-prefs.json")