Use constants.

Runtime/editor/editor_window.cs

 
         bool _alive;
 
-        Timer scheduleFrameTimer = null;
+        Timer scheduleFrameTimer;
+        const int maxTargetFrameRate = 60;
+        const int minTargetFrameRate = 15;
+        const int targetFrameRateAdaptStep = 10;
 
         public bool alive {
             get { return this._alive; }
             if (regenerateLayerTree) {
                 this._regenerateLayerTree = true;
             }
-            Application.targetFrameRate = 60;
+            Application.targetFrameRate = maxTargetFrameRate;
-                    if (Application.targetFrameRate > 10)
-                        Application.targetFrameRate -= 10;
+                    if (Application.targetFrameRate > minTargetFrameRate)
+                        Application.targetFrameRate -= targetFrameRateAdaptStep;
-                        Application.targetFrameRate = 10;
+                        Application.targetFrameRate = minTargetFrameRate;
                         this.scheduleFrameTimer.cancel();
                         this.scheduleFrameTimer = null;
                     }