Add PartitionAllocGigaCage finch config to fieldtrial_testing_config.json

Bug: 1086388
Change-Id: I6d10c4f8289cc6555f5d71a664fbc3d3d677ca7c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2498023Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Bartek Nowierski <bartekn@chromium.org>
Commit-Queue: Takashi Sakamoto <tasak@google.com>
Cr-Commit-Position: refs/heads/master@{#821081}

testing/variations/fieldtrial_testing_config.json

@@ -5177,6 +5177,26 @@
             ]
         }
     ],
+    "PartitionAllocGigaCage": [
+        {
+            "platforms": [
+                "android",
+                "android_webview",
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "PartitionAllocGigaCage"
+                    ]
+                }
+            ]
+        }
+    ],
     "PartitionConnectionsByNetworkIsolationKey": [
         {
             "platforms": [