Delete MessageData when a message is posted to a quitting MessageQueue

Bug: webrtc:9913
Change-Id: Id60f537eb0049995c9f0837e3a03ca3a3dd90577
Reviewed-on: https://webrtc-review.googlesource.com/c/107639
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25365}

rtc_base/messagequeue.cc

@@ -350,8 +350,10 @@ void MessageQueue::Post(const Location& posted_from,
                         uint32_t id,
                         MessageData* pdata,
                         bool time_sensitive) {
-  if (IsQuitting())
+  if (IsQuitting()) {
+    delete pdata;
     return;
+  }
 
   // Keep thread safe
   // Add the message to the end of the queue
@@ -407,6 +409,7 @@ void MessageQueue::DoDelayPost(const Location& posted_from,
                                uint32_t id,
                                MessageData* pdata) {
   if (IsQuitting()) {
+    delete pdata;
     return;
   }