Reland of Fix typo in Android perf variations for unified media pipeline trial.

testing/variations/fieldtrial_testing_config_android.json

 {
     "AndroidSessionNotifications": [
         {
             "group_name": "Disabled"
         }
     ],
     "AsyncDns": [
         {
             "group_name": "AsyncDnsA"
         },
@@ skipping 363 matching lines @@
     "UMA_EnableCellularLogUpload": [
         {
             "group_name": "Enabled_wo_sampling",
             "params": {
                 "Enabled": "true",
                 "Optimize": "true",
                 "Sample_Probability": "100"
             }
         }
     ],
-    "UnifiedMediaPipeline": [
+    "UnifiedMediaPipelineTrial": [
         {
             "group_name": "Enabled"
         }
     ],
     "UpdateMenuItem": [
         {
             "group_name": "Enabled",
             "params": {
                 "enable_update_menu_item": "true"
             }
@@ skipping 60 matching lines @@
     ],
     "use-new-media-cache": [
         {
             "enable_features": [
                 "use-new-media-cache"
             ],
             "group_name": "Enabled"
         }
     ]
 }