[Sync] Finch Experiment : Enable compression between sync client and server

testing/variations/fieldtrial_testing_config_android.json

 {
     "EnhancedBookmarks": [
         {
             "group_name": "EnableEnhancedBookmarks",
             "params": {
                 "id": "Fake_id_to_trigger_experiment_code"
             }
         },
         {
             "group_name": "EnableEnhancedBookmarksGrid",
@@ skipping 170 matching lines @@
             "group_name":
                 "v=1e:Prefetching=Enabled:Predictor=Host:Confidence=High"
         },
         {
             "group_name":
                 "v=1f:Prefetching=Enabled:Predictor=Host:Confidence=Low"
         },
         {
             "group_name": "v=1:Prefetching=Learning"
         }
+    ],
+    "SyncHttpContentCompression": [
+        {
+            "group_name": "Enabled"
+        },
+        {
+            "group_name": "Disabled"
+        }
     ]
 }