From 516473dbba6bb64d20862541970083b1f6121cf8 Mon Sep 17 00:00:00 2001
From: Jia Hao Goh <jiahaog@users.noreply.github.com>
Date: Thu, 19 Oct 2023 08:34:01 +0800
Subject: [PATCH] Add missing import

Fixes the following:

https://github.com/flutter/engine/commit/6b262a0529bea8c58eb763fe15bd8d647dd07641 results in the following error appearing internally when compiling for Android:

```
In file included from fml/synchronization/sync_switch.cc:5:
./fml/synchronization/sync_switch.h:74:34: error: implicit instantiation of undefined template 'std::vector<fml::SyncSwitch::Observer *>'
  mutable std::vector<Observer*> observers_;
                                 ^
<...>: note: template is declared here
class _LIBCPP_TEMPLATE_VIS vector;
                           ^
1 error generated.
```
---
 fml/synchronization/sync_switch.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fml/synchronization/sync_switch.h b/fml/synchronization/sync_switch.h
index c01c05aac25ff..d9b0807afd9c3 100644
--- a/fml/synchronization/sync_switch.h
+++ b/fml/synchronization/sync_switch.h
@@ -5,9 +5,9 @@
 #ifndef FLUTTER_FML_SYNCHRONIZATION_SYNC_SWITCH_H_
 #define FLUTTER_FML_SYNCHRONIZATION_SYNC_SWITCH_H_
 
-#include <forward_list>
 #include <functional>
 #include <memory>
+#include <vector>
 
 #include "flutter/fml/macros.h"
 #include "flutter/fml/synchronization/shared_mutex.h"