[scheduler] Enable expensive background timer throttling on waterfall.

testing/variations/fieldtrial_testing_config.json

Index: testing/variations/fieldtrial_testing_config.json
diff --git a/testing/variations/fieldtrial_testing_config.json b/testing/variations/fieldtrial_testing_config.json
index 197e76822001d19f674e28d364eb17f11f0615ae..3bf5a94fb15f24bd2bb31e59546912f3d5e5f8e3 100644
--- a/testing/variations/fieldtrial_testing_config.json
+++ b/testing/variations/fieldtrial_testing_config.json
@@ -664,6 +664,31 @@
             ]
         }
     ],
+    "ExpensiveBackgroundTimerThrottling": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "linux",
+                "mac",
+                "win"
+            ],
+            "experiments": [
+                {
+                    "name": "ExpensiveBackgroundTimerThrottlingEnabled",
+                    "params": {
+                        "cpu_budget": "0.01",
+                        "initial_budget": "1.0",
+                        "max_budget": "3.0",
+                        "max_delay": "-1"
+                    },
+                    "enable_features": [
+                        "ExpensiveBackgroundTimerThrottling"
+                    ]
+                }
+            ]
+        }
+    ],
     "ExtensionActionRedesign": [
         {
             "platforms": [