Enable pointer events on waterfall.

testing/variations/fieldtrial_testing_config_android.json

 {
     "AndroidSessionNotifications": [
         {
             "group_name": "Disabled"
         }
     ],
     "AsyncDns": [
         {
             "group_name": "AsyncDnsA"
         },
@@ skipping 252 matching lines @@
         }
     ],
     "PhysicalWeb": [
         {
             "enable_features": [
                 "PhysicalWeb"
             ],
             "group_name": "Enabled"
         }
     ],
+    "PointerEvent": [
+        {
+            "enable_features": [
+                "PointerEvent"
+            ],
+            "group_name": "Enabled"
+        }
+    ],
     "Precache": [
         {
             "group_name": "Enabled"
         }
     ],
     "PreconnectMore": [
         {
             "enable_features": [
                 "PreconnectMore"
             ],
@@ skipping 254 matching lines @@
     ],
     "use-new-media-cache": [
         {
             "enable_features": [
                 "use-new-media-cache"
             ],
             "group_name": "Enabled"
         }
     ]
 }