Fix ASAN crash in RCTMessageThread

Summary:
This should fix a race condition uncovered by ASAN build that results in `m_shutdown` being referenced after destruction.

This mirrors a similar fix made in react-native-macos: ea7767a211

Changelog: [Internal]

Reviewed By: shergin

Differential Revision: D24263156

fbshipit-source-id: 5fb1e7053c107dfb7050242fce8fcf0435e5592c

React/CxxBridge/RCTMessageThread.h

@@ -5,6 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+#import <memory>
 #import <string>
 
 #import <Foundation/Foundation.h>
@@ -15,7 +16,8 @@
 namespace facebook {
 namespace react {
 
-class RCTMessageThread : public MessageQueueThread {
+class RCTMessageThread : public MessageQueueThread,
+                         public std::enable_shared_from_this<RCTMessageThread> {
  public:
   RCTMessageThread(NSRunLoop *runLoop, RCTJavaScriptCompleteBlock errorBlock);
   ~RCTMessageThread() override;

React/CxxBridge/RCTMessageThread.mm

@@ -31,6 +31,7 @@ RCTMessageThread::RCTMessageThread(NSRunLoop *runLoop, RCTJavaScriptCompleteBloc
 
 RCTMessageThread::~RCTMessageThread()
 {
+  RCTAssert(m_shutdown, @"RCTMessageThread: quitSynchronous() not called before destructor");
   CFRelease(m_cfRunLoop);
 }
 
@@ -76,10 +77,9 @@ void RCTMessageThread::runOnQueue(std::function<void()> &&func)
   if (m_shutdown) {
     return;
   }
-
-  runAsync([this, func = std::make_shared<std::function<void()>>(std::move(func))] {
-    if (!m_shutdown) {
-      tryFunc(*func);
+  runAsync([sharedThis = shared_from_this(), func = std::make_shared<std::function<void()>>(std::move(func))] {
+    if (!sharedThis->m_shutdown) {
+      sharedThis->tryFunc(*func);
     }
   });
 }
@@ -89,9 +89,9 @@ void RCTMessageThread::runOnQueueSync(std::function<void()> &&func)
   if (m_shutdown) {
     return;
   }
-  runSync([this, func = std::move(func)] {
-    if (!m_shutdown) {
-      tryFunc(func);
+  runSync([sharedThis = shared_from_this(), func = std::move(func)] {
+    if (!sharedThis->m_shutdown) {
+      sharedThis->tryFunc(func);
     }
   });
 }