[v8] Add off-thread finalization field trial

Bug: chromium:1011762
Change-Id: I6cc384b5815fb67ccbf516fc358e2825a2fc777f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2501622
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Brian White <bcwhite@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821441}

testing/variations/fieldtrial_testing_config.json

@@ -7370,6 +7370,25 @@
             ]
         }
     ],
+    "V8OffThreadFinalization": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "V8OffThreadFinalization"
+                    ]
+                }
+            ]
+        }
+    ],
     "VideoToolboxVp9Decoding": [
         {
             "platforms": [