Add AsyncNavigationIntercept to fieldtrial_testing_config

Bug: 793053
Change-Id: I0d39cd8e6695b18da47549e632f10abd9919c83e
Reviewed-on: https://chromium-review.googlesource.com/1106519Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568829}

testing/variations/fieldtrial_testing_config.json

@@ -350,6 +350,21 @@
             ]
         }
     ],
+    "AsyncNavigationIntercept": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "AsyncNavigationIntercept"
+                    ]
+                }
+            ]
+        }
+    ],
     "AudioService": [
         {
             "platforms": [