Added marshalling to main thread messages sent from native side

AUTHORS

@@ -16,3 +16,4 @@ Stanislav Shmarov <github@snarpix.com>
 Sebastian Urban <surban@surban.net>
 Ómar Högni Guðmarsson <ohg@skaginn3x.com>
 Athaariq Ardhiansyah <foss@athaariq.my.id>
+Anton Sakhon <kofhein@gmail.com>

src/flutter/shell/platform/common/client_wrapper/core_implementations.cc

@@ -66,6 +66,11 @@ BinaryMessengerImpl::BinaryMessengerImpl(
 
 BinaryMessengerImpl::~BinaryMessengerImpl() = default;
 
+void CaptureCleaner(void* lambda) {
+  auto& cleanup = *reinterpret_cast<std::function<void()>*>(lambda);
+  cleanup();
+}
+
 void BinaryMessengerImpl::Send(const std::string& channel,
                                const uint8_t* message,
                                size_t message_size,
@@ -89,10 +94,10 @@ void BinaryMessengerImpl::Send(const std::string& channel,
   };
   bool result = FlutterDesktopMessengerSendWithReply(
       messenger_, channel.c_str(), message, message_size, message_reply,
-      captures);
-  if (!result) {
-    delete captures;
-  }
+      captures, [](void* captures_data) {
+        auto captures = reinterpret_cast<Captures*>(captures_data);
+        delete captures;
+      });
 }
 
 void BinaryMessengerImpl::SetMessageHandler(const std::string& channel,

src/flutter/shell/platform/common/public/flutter_messenger.h

@@ -63,7 +63,8 @@ FLUTTER_EXPORT bool FlutterDesktopMessengerSendWithReply(
     const uint8_t* message,
     const size_t message_size,
     const FlutterDesktopBinaryReply reply,
-    void* user_data);
+    void* user_data,
+    void (*cleanup)(void* captures_data));
 
 // Sends a reply to a FlutterDesktopMessage for the given response handle.
 //

src/flutter/shell/platform/linux_embedded/flutter_elinux.cc

@@ -199,22 +199,36 @@ void FlutterDesktopPluginRegistrarSetDestructionHandler(
   registrar->engine->SetPluginRegistrarDestructionCallback(callback);
 }
 
-bool FlutterDesktopMessengerSendWithReply(FlutterDesktopMessengerRef messenger,
-                                          const char* channel,
-                                          const uint8_t* message,
-                                          const size_t message_size,
-                                          const FlutterDesktopBinaryReply reply,
-                                          void* user_data) {
-  return messenger->GetEngine()->SendPlatformMessage(
-      channel, message, message_size, reply, user_data);
+bool FlutterDesktopMessengerSendWithReply(
+    FlutterDesktopMessengerRef messenger,
+    const char* channel,
+    const uint8_t* message,
+    const size_t message_size,
+    const FlutterDesktopBinaryReply reply,
+    void* user_data,
+    void (*cleanup)(void* captures_data)) {
+  // As we pass data to lambda and it's pointers we need to make sure that we
+  // send valid data
+  std::string channel_copy(channel);
+  std::vector<uint8_t> message_copy(message, message + message_size);
+
+  messenger->GetEngine()->task_runner()->PostTask([=]() {
+    if (!messenger->GetEngine()->SendPlatformMessage(
+            channel_copy.c_str(), message_copy.data(), message_copy.size(),
+            reply, user_data) &&
+        user_data) {
+      cleanup(user_data);
+    }
+  });
+  return true;
 }
 
 bool FlutterDesktopMessengerSend(FlutterDesktopMessengerRef messenger,
                                  const char* channel,
                                  const uint8_t* message,
                                  const size_t message_size) {
-  return FlutterDesktopMessengerSendWithReply(messenger, channel, message,
-                                              message_size, nullptr, nullptr);
+  return FlutterDesktopMessengerSendWithReply(
+      messenger, channel, message, message_size, nullptr, nullptr, nullptr);
 }
 
 void FlutterDesktopMessengerSendResponse(