Enable V4LocalDatabaseManager based on Finch.

testing/variations/fieldtrial_testing_config_win.json

 {
     "AutofillClassifier": [
         {
             "group_name": "Enabled"
         }
     ],
     "AutofillFieldMetadata": [
         {
             "group_name": "Enabled"
         }
@@ skipping 308 matching lines @@
         }
     ],
     "SafeBrowsingUpdateFrequency": [
         {
             "group_name": "UpdateTime15m",
             "params": {
                 "NextUpdateIntervalInMinutes": "15"
             }
         }
     ],
+    "SafeBrowsingV4LocalDatabaseManagerEnabled": [
+        {
+            "group_name": "Enabled"

[rkaplow, 2016/05/02 16:27:35]

you only needed one group here to be tested. Likely it should be enabled which
is the main group experimented on.

[vakh (use Gerrit instead), 2016/05/02 22:04:34]

Done.

+        },
+        {
+            "group_name": "Disabled"
+        },
+        {
+            "group_name": "Default"
+        }
+    ],
     "SchedulerExpensiveTaskBlocking": [
         {
             "group_name": "Enabled"
         }
     ],
     "SdchPersistence": [
         {
             "group_name": "Enabled"
         }
     ],
@@ skipping 66 matching lines @@
     ],
     "use-new-media-cache": [
         {
             "enable_features": [
                 "use-new-media-cache"
             ],
             "group_name": "Enabled"
         }
     ]
 }