store [nfc]: Move debugEnableRegisterNotificationToken to end of class

We'll need another of these for fetching emoji data.  Let's move them
out from amidst all the main logic, to keep down the clutter.

Author: gnprice

lib/model/store.dart

@@ -865,26 +865,6 @@ class UpdateMachine {
     }
   }
 
-  /// In debug mode, controls whether [registerNotificationToken] should
-  /// have its normal effect.
-  ///
-  /// Outside of debug mode, this is always true and the setter has no effect.
-  static bool get debugEnableRegisterNotificationToken {
-    bool result = true;
-    assert(() {
-      result = _debugEnableRegisterNotificationToken;
-      return true;
-    }());
-    return result;
-  }
-  static bool _debugEnableRegisterNotificationToken = true;
-  static set debugEnableRegisterNotificationToken(bool value) {
-    assert(() {
-      _debugEnableRegisterNotificationToken = value;
-      return true;
-    }());
-  }
-
   /// Send this client's notification token to the server, now and if it changes.
   ///
   /// TODO The returned future isn't especially meaningful (it may or may not
@@ -910,6 +890,26 @@ class UpdateMachine {
     NotificationService.instance.token.removeListener(_registerNotificationToken);
   }
 
+  /// In debug mode, controls whether [registerNotificationToken] should
+  /// have its normal effect.
+  ///
+  /// Outside of debug mode, this is always true and the setter has no effect.
+  static bool get debugEnableRegisterNotificationToken {
+    bool result = true;
+    assert(() {
+      result = _debugEnableRegisterNotificationToken;
+      return true;
+    }());
+    return result;
+  }
+  static bool _debugEnableRegisterNotificationToken = true;
+  static set debugEnableRegisterNotificationToken(bool value) {
+    assert(() {
+      _debugEnableRegisterNotificationToken = value;
+      return true;
+    }());
+  }
+
   @override
   String toString() => '${objectRuntimeType(this, 'UpdateMachine')}#${shortHash(this)}';
 }