Use UIWidgetsGlobalSettings.

Runtime/editor/editor_window.cs

 using System;
 using System.Collections.Generic;
 using Unity.UIWidgets.async;
+using Unity.UIWidgets.engine;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.rendering;
 using Unity.UIWidgets.scheduler;
             if (regenerateLayerTree) {
                 this._regenerateLayerTree = true;
             }
+            UIWidgetsGlobalSettings.instance.speedUpFrameRate();
+            UIWidgetsGlobalSettings.instance.coolDownFrameRate();
         }
 
         public override void render(Scene scene) {

Runtime/engine/UIWidgetsPanel.cs

         public override void scheduleFrame(bool regenerateLayerTree = true) {
             base.scheduleFrame(regenerateLayerTree);
             this._needsPaint = true;
-            this._uiWidgetsPanel.speedUpFrameRate();
-            this._uiWidgetsPanel.coolDownFrameRate();
         }
 
         public UIWidgetWindowAdapter(UIWidgetsPanel uiWidgetsPanel) {
         Texture _texture;
         Vector2 _lastMouseMove;
         
-        Timer scheduleFrameTimer;
-        public const int defaultMaxTargetFrameRate = 60;
-        public const int defaultMinTargetFrameRate = 15;
-
         readonly HashSet<int> _enteredPointers = new HashSet<int>();
 
         bool _viewMetricsCallbackRegistered;
 
         public Window window {
             get { return this._windowAdapter; }
-        }
-
-        public virtual void speedUpFrameRate() {
-            Application.targetFrameRate = defaultMaxTargetFrameRate;
-        }
-
-        public virtual void coolDownFrameRate() {
-            this.scheduleFrameTimer?.cancel();
-            this.scheduleFrameTimer = this.window.run(
-                new TimeSpan(0, 0, 0, 0, 200),
-                () => {
-                    Application.targetFrameRate = defaultMinTargetFrameRate;
-                    this.scheduleFrameTimer = null;
-                });
         }
     }
 }

Runtime/engine/global_settings.cs

+using System;
+using Unity.UIWidgets.async;
+using Unity.UIWidgets.ui;
+using UnityEngine;
+
+namespace Unity.UIWidgets.engine {
+    public class UIWidgetsGlobalSettings {
+        private UIWidgetsGlobalSettings() {}
+        
+        static UIWidgetsGlobalSettings _instance = new UIWidgetsGlobalSettings();
+        Timer scheduleFrameTimer;
+        public const int defaultMaxTargetFrameRate = 60;
+        public const int defaultMinTargetFrameRate = 15;
+
+
+        public static UIWidgetsGlobalSettings instance {
+            get { return _instance; }
+        }
+
+        public virtual void speedUpFrameRate() {
+            Application.targetFrameRate = defaultMaxTargetFrameRate;
+        }
+
+        public virtual void coolDownFrameRate() {
+            this.scheduleFrameTimer?.cancel();
+            this.scheduleFrameTimer = Window.instance.run(
+                new TimeSpan(0, 0, 0, 0, 200),
+                () => {
+                    Application.targetFrameRate = defaultMinTargetFrameRate;
+                    this.scheduleFrameTimer = null;
+                });
+        }
+    }
+}

Runtime/engine/global_settings.cs.meta

+fileFormatVersion: 2
+guid: 3ffd4ed5bc5c4758b56f365a50418fff
+timeCreated: 1554884592