Enable DownloadRename flag in experiments

Bug: 924751
Change-Id: Ibebb57791014be59a0c261deb715b9a1e09acba1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1633333Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Hesen Zhang <hesen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664780}

testing/variations/fieldtrial_testing_config.json

@@ -1879,6 +1879,21 @@
             ]
         }
     ],
+    "DownloadRename": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "DownloadRename"
+                    ]
+                }
+            ]
+        }
+    ],
     "DownloadsLocationChange": [
         {
             "platforms": [