Add fieldtrial testing config for leveldb_proto

Bug: 870813
Change-Id: I01b36a864a3c573bc5ef392f88180e27206fdeb4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1914961Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Salvador Guerrero <salg@google.com>
Cr-Commit-Position: refs/heads/master@{#715342}

testing/variations/fieldtrial_testing_config.json

@@ -5002,6 +5002,51 @@
             ]
         }
     ],
+    "ProtoDBSharedMigration": [
+        {
+            "platforms": [
+                "android_webview",
+                "android",
+                "chromeos",
+                "ios",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled3",
+                    "params": {
+                        "migrate_BudgetManager": "true",
+                        "migrate_CachedImageFetcherDatabase": "true",
+                        "migrate_DomDistillerStore": "true",
+                        "migrate_DownloadDB": "true",
+                        "migrate_DownloadService": "true",
+                        "migrate_FeatureEngagementTrackerAvailabilityStore": "true",
+                        "migrate_FeatureEngagementTrackerEventStore": "true",
+                        "migrate_FeedContentDatabase": "true",
+                        "migrate_FeedJournalDatabase": "true",
+                        "migrate_GCMKeyStore": "true",
+                        "migrate_NTPSnippetImages": "true",
+                        "migrate_NTPSnippets": "true",
+                        "migrate_PreviewsHintCacheStore": "true",
+                        "migrate_PrintJobDatabase": "true",
+                        "migrate_StrikeService": "true",
+                        "migrate_TestDatabase0": "true",
+                        "migrate_TestDatabase1": "true",
+                        "migrate_TestDatabase2": "true",
+                        "migrate_UsageStatsSuspension": "true",
+                        "migrate_UsageStatsTokenMapping": "true",
+                        "migrate_UsageStatsWebsiteEvent": "true",
+                        "migrate_VideoDecodeStatsDB": "true"
+                    },
+                    "enable_features": [
+                        "ProtoDBSharedMigration"
+                    ]
+                }
+            ]
+        }
+    ],
     "QUIC": [
         {
             "platforms": [