Started logging warnings if we drop platform messages. (#11792)

lib/ui/window/window.cc

@@ -261,13 +261,21 @@ void Window::UpdateAccessibilityFeatures(int32_t values) {
 
 void Window::DispatchPlatformMessage(fml::RefPtr<PlatformMessage> message) {
   std::shared_ptr<tonic::DartState> dart_state = library_.dart_state().lock();
-  if (!dart_state)
+  if (!dart_state) {
+    FML_DLOG(WARNING)
+        << "Dropping platform message for lack of DartState on channel: "
+        << message->channel();
     return;
+  }
   tonic::DartState::Scope scope(dart_state);
   Dart_Handle data_handle =
       (message->hasData()) ? ToByteData(message->data()) : Dart_Null();
-  if (Dart_IsError(data_handle))
+  if (Dart_IsError(data_handle)) {
+    FML_DLOG(WARNING)
+        << "Dropping platform message because of a Dart error on channel: "
+        << message->channel();
     return;
+  }
 
   int response_id = 0;
   if (auto response = message->response()) {

shell/common/engine.cc

@@ -288,8 +288,13 @@ void Engine::DispatchPlatformMessage(fml::RefPtr<PlatformMessage> message) {
   }
 
   // If there's no runtime_, we may still need to set the initial route.
-  if (message->channel() == kNavigationChannel)
+  if (message->channel() == kNavigationChannel) {
     HandleNavigationPlatformMessage(std::move(message));
+    return;
+  }
+
+  FML_DLOG(WARNING) << "Dropping platform message on channel: "
+                    << message->channel();
 }
 
 bool Engine::HandleLifecyclePlatformMessage(PlatformMessage* message) {