Sign-in promo in the password bubble: test dismissal_threshold=3 on the waterfall.

testing/variations/fieldtrial_testing_config.json

 {
     "AndroidSessionNotifications": [
         {
             "platforms": [
                 "android"
             ],
             "experiments": [
                 {
                     "name": "Disabled"
                 }
@@ skipping 1866 matching lines @@
     ],
     "SignInPasswordPromo": [
         {
             "platforms": [
                 "linux",
                 "mac",
                 "win"
             ],
             "experiments": [
                 {
-                    "name": "Enable2",
+                    "name": "Enable3",
                     "params": {
-                        "dismissal_threshold": "2"
+                        "dismissal_threshold": "3"
                     }
                 }
             ]
         }
     ],
     "SimpleCacheTrial": [
         {
             "platforms": [
                 "chromeos",
                 "linux",
@@ skipping 439 matching lines @@
                 {
                     "name": "Enabled",
                     "enable_features": [
                         "use-new-media-cache"
                     ]
                 }
             ]
         }
     ]
 }