Add PreconnectOnDidFinishNavigation entry to FTTC

Add PreconnectOnDidFinishNavigation entry to field trial testing config.
The 3 second arm is chosen as it is the most likely to launch.

Bug: 1016553
Change-Id: I84250e6d4ef55edc988de2edf2a2c873dd61d22f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1900470Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714383}

testing/variations/fieldtrial_testing_config.json

@@ -4711,6 +4711,24 @@
             ]
         }
     ],
+    "PreconnectOnDidFinishNavigation": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled_3_seconds",
+                    "params": {
+                        "delay_after_commit_in_ms": "3000"
+                    },
+                    "enable_features": [
+                        "PreconnectOnDidFinishNavigation"
+                    ]
+                }
+            ]
+        }
+    ],
     "PrefetchSRPAndroid": [
         {
             "platforms": [