Add calls to Dart_NotifyDestroyed when the flutter view is destroyed.

Author: a-siva

runtime/runtime_controller.cc

@@ -235,6 +235,19 @@ bool RuntimeController::NotifyIdle(fml::TimePoint deadline) {
   return true;
 }
 
+bool RuntimeController::NotifyDestroyed() {
+  std::shared_ptr<DartIsolate> root_isolate = root_isolate_.lock();
+  if (!root_isolate) {
+    return false;
+  }
+
+  tonic::DartState::Scope scope(root_isolate);
+
+  Dart_NotifyDestroyed();
+
+  return true;
+}
+
 bool RuntimeController::DispatchPlatformMessage(
     std::unique_ptr<PlatformMessage> message) {
   if (auto* platform_configuration = GetPlatformConfigurationIfAvailable()) {

runtime/runtime_controller.h

@@ -360,6 +360,17 @@ class RuntimeController : public PlatformConfigurationClient {
   ///
   virtual bool NotifyIdle(fml::TimePoint deadline);
 
+  //----------------------------------------------------------------------------
+  /// @brief      Notify the Dart VM that the attached flutter view has been
+  ///             destroyed. This gives the Dart VM to perform some cleanup
+  ///             activities e.g: perform garbage collection to free up any
+  ///             unused memory.
+  ///
+  /// NotifyDestroyed is advisory. The VM may or may not perform any clean up
+  /// activities.
+  ///
+  virtual bool NotifyDestroyed();
+
   //----------------------------------------------------------------------------
   /// @brief      Returns if the root isolate is running. The isolate must be
   ///             transitioned to the running phase manually. The isolate can

shell/common/engine.cc

@@ -266,6 +266,11 @@ void Engine::NotifyIdle(fml::TimePoint deadline) {
   runtime_controller_->NotifyIdle(deadline);
 }
 
+void Engine::NotifyDestroyed() {
+  TRACE_EVENT0("flutter", "Engine::NotifyDestroyed");
+  runtime_controller_->NotifyDestroyed();
+}
+
 std::optional<uint32_t> Engine::GetUIIsolateReturnCode() {
   return runtime_controller_->GetRootIsolateReturnCode();
 }

shell/common/engine.h

@@ -554,6 +554,13 @@ class Engine final : public RuntimeDelegate, PointerDataDispatcher::Delegate {
   ///
   void NotifyIdle(fml::TimePoint deadline);
 
+  //----------------------------------------------------------------------------
+  /// @brief      Notifies the engine that the attached flutter view has been
+  ///             destroyed.
+  ///             This enables the engine to notify the Dart VM so it can do
+  ///             some cleanp activities.
+  void NotifyDestroyed();
+
   //----------------------------------------------------------------------------
   /// @brief      Dart code cannot fully measure the time it takes for a
   ///             specific frame to be rendered. This is because Dart code only

shell/common/shell.cc

@@ -899,6 +899,12 @@ void Shell::OnPlatformViewDestroyed() {
   // Overall, the longer term plan is to remove this implementation once
   // https://github.com/flutter/flutter/issues/96679 is fixed.
   rasterizer_->TeardownExternalViewEmbedder();
+
+  auto ui_task = [engine = engine_->GetWeakPtr()] {
+    if (engine) {
+      engine->NotifyDestroyed();
+    }
+  };
 }
 
 // |PlatformView::Delegate|