Attempt to fix crash during app termination

Summary:
changelog: Attempt to fix a crash during app termination on iOS in the new renderer

We need to stop all surfaces before it is terminated to prevent app from crashing.

The crash happens on background thread.
The app crashes because it is probably accessing static variable that has been deallocated by the main thread. How can main thread deallocate things when background thread is still running? Because main thread is attached to our app's process, background thread is provided by the system and continues to live.

Reviewed By: ShikaSD

Differential Revision: D33977161

fbshipit-source-id: 87546d7b70d1aa465e63f0d37b70bae1fffa2304

React/Fabric/RCTSurfacePresenter.mm

@@ -99,6 +99,14 @@ static BackgroundExecutor RCTGetBackgroundExecutor()
     _observers = [NSMutableArray array];
 
     _scheduler = [self _createScheduler];
+
+    auto reactNativeConfig = _contextContainer->at<std::shared_ptr<ReactNativeConfig const>>("ReactNativeConfig");
+    if (reactNativeConfig->getBool("react_native_new_architecture:suspend_before_app_termination")) {
+      [[NSNotificationCenter defaultCenter] addObserver:self
+                                               selector:@selector(_applicationWillTerminate)
+                                                   name:UIApplicationWillTerminateNotification
+                                                 object:nil];
+    }
   }
 
   return self;
@@ -327,6 +335,11 @@ static BackgroundExecutor RCTGetBackgroundExecutor()
   }];
 }
 
+- (void)_applicationWillTerminate
+{
+  [self suspend];
+}
+
 #pragma mark - RCTSchedulerDelegate
 
 - (void)schedulerDidFinishTransaction:(MountingCoordinator::Shared const &)mountingCoordinator