Add Finch testing config for PasswordBranding

testing/variations/fieldtrial_testing_config_android.json

 {
     "AndroidSessionNotifications": [
         {
             "group_name": "Disabled"
         }
     ],
     "AutodetectEncoding": [
         {
             "group_name": "Enabled"
         }
@@ skipping 184 matching lines @@
                 "HalfLifeSeconds": "60",
                 "None.DefaultMedianKbps": "567",
                 "None.DefaultMedianRTTMsec": "272",
                 "Unknown.DefaultMedianKbps": "1916",
                 "Unknown.DefaultMedianRTTMsec": "121",
                 "WiFi.DefaultMedianKbps": "2736",
                 "WiFi.DefaultMedianRTTMsec": "168"
             }
         }
     ],
+    "PasswordBranding": [
+        {
+            "group_name": "SmartLockBranding"
+        }
+    ],
     "Precache": [
         {
             "group_name": "Enabled"
         }
     ],
     "ProgressBarAnimationAndroid": [
         {
             "group_name": "SmoothAnimation",
             "params": {
                 "progress-bar-animation": "smooth"
@@ skipping 180 matching lines @@
         {
             "group_name": "Enabled"
         }
     ],
     "WebRTC-PeerConnectionDTLS1.2": [
         {
             "group_name": "Enabled"
         }
     ]
 }