Avoid dereferencing IO manager weak pointers on the UI thread (#13232)

UI thread APIs that need to access the IO thread's resource context should
obtain a weak pointer to the IO manager and pass that to the IO thread.

Author: jason-simmons

lib/ui/painting/image_encoding.cc

@@ -211,21 +211,16 @@ Dart_Handle EncodeImage(CanvasImage* canvas_image,
       tonic::DartState::Current(), callback_handle);
 
   const auto& task_runners = UIDartState::Current()->GetTaskRunners();
-  auto context = UIDartState::Current()->GetResourceContext();
-
-  task_runners.GetIOTaskRunner()->PostTask(
-      fml::MakeCopyable([callback = std::move(callback),                   //
-                         image = canvas_image->image(),                    //
-                         context = std::move(context),                     //
-                         ui_task_runner = task_runners.GetUITaskRunner(),  //
-                         image_format                                      //
-  ]() mutable {
-        EncodeImageAndInvokeDataCallback(std::move(callback),        //
-                                         std::move(image),           //
-                                         context.get(),              //
-                                         std::move(ui_task_runner),  //
-                                         image_format                //
-        );
+
+  task_runners.GetIOTaskRunner()->PostTask(fml::MakeCopyable(
+      [callback = std::move(callback), image = canvas_image->image(),
+       io_manager = UIDartState::Current()->GetIOManager(),
+       ui_task_runner = task_runners.GetUITaskRunner(),
+       image_format]() mutable {
+        EncodeImageAndInvokeDataCallback(std::move(callback), std::move(image),
+                                         io_manager->GetResourceContext().get(),
+                                         std::move(ui_task_runner),
+                                         image_format);
       }));
 
   return Dart_Null();

lib/ui/painting/multi_frame_codec.cc

@@ -168,11 +168,11 @@ Dart_Handle MultiFrameCodec::getNextFrame(Dart_Handle callback_handle) {
       [callback = std::make_unique<DartPersistentValue>(
            tonic::DartState::Current(), callback_handle),
        this, trace_id, ui_task_runner = task_runners.GetUITaskRunner(),
-       queue = UIDartState::Current()->GetSkiaUnrefQueue(),
-       context = dart_state->GetResourceContext()]() mutable {
-        GetNextFrameAndInvokeCallback(std::move(callback),
-                                      std::move(ui_task_runner), context,
-                                      std::move(queue), trace_id);
+       io_manager = dart_state->GetIOManager()]() mutable {
+        GetNextFrameAndInvokeCallback(
+            std::move(callback), std::move(ui_task_runner),
+            io_manager->GetResourceContext(), io_manager->GetSkiaUnrefQueue(),
+            trace_id);
       }));
 
   return Dart_Null();

lib/ui/painting/picture.cc

@@ -136,7 +136,7 @@ Dart_Handle Picture::RasterizeToImage(sk_sp<SkPicture> picture,
   auto unref_queue = dart_state->GetSkiaUnrefQueue();
   auto ui_task_runner = dart_state->GetTaskRunners().GetUITaskRunner();
   auto io_task_runner = dart_state->GetTaskRunners().GetIOTaskRunner();
-  fml::WeakPtr<GrContext> resource_context = dart_state->GetResourceContext();
+  fml::WeakPtr<IOManager> io_manager = dart_state->GetIOManager();
 
   // We can't create an image on this task runner because we don't have a
   // graphics context. Even if we did, it would be slow anyway. Also, this
@@ -173,9 +173,9 @@ Dart_Handle Picture::RasterizeToImage(sk_sp<SkPicture> picture,
 
   fml::TaskRunner::RunNowOrPostTask(io_task_runner, [ui_task_runner, picture,
                                                      picture_bounds, ui_task,
-                                                     resource_context] {
+                                                     io_manager] {
     sk_sp<SkSurface> surface =
-        MakeSnapshotSurface(picture_bounds, resource_context);
+        MakeSnapshotSurface(picture_bounds, io_manager->GetResourceContext());
     sk_sp<SkImage> raster_image = MakeRasterSnapshot(picture, surface);
 
     fml::TaskRunner::RunNowOrPostTask(

lib/ui/ui_dart_state.cc

@@ -78,6 +78,10 @@ const TaskRunners& UIDartState::GetTaskRunners() const {
   return task_runners_;
 }
 
+fml::WeakPtr<IOManager> UIDartState::GetIOManager() const {
+  return io_manager_;
+}
+
 fml::RefPtr<flutter::SkiaUnrefQueue> UIDartState::GetSkiaUnrefQueue() const {
   // TODO(gw280): The WeakPtr here asserts that we are derefing it on the
   // same thread as it was created on. As we can't guarantee that currently
@@ -119,14 +123,6 @@ void UIDartState::AddOrRemoveTaskObserver(bool add) {
   }
 }
 
-fml::WeakPtr<GrContext> UIDartState::GetResourceContext() const {
-  FML_DCHECK(task_runners_.GetIOTaskRunner()->RunsTasksOnCurrentThread());
-  if (!io_manager_) {
-    return {};
-  }
-  return io_manager_->GetResourceContext();
-}
-
 fml::WeakPtr<ImageDecoder> UIDartState::GetImageDecoder() const {
   return image_decoder_;
 }

lib/ui/ui_dart_state.h

@@ -48,9 +48,9 @@ class UIDartState : public tonic::DartState {
 
   void FlushMicrotasksNow();
 
-  fml::RefPtr<flutter::SkiaUnrefQueue> GetSkiaUnrefQueue() const;
+  fml::WeakPtr<IOManager> GetIOManager() const;
 
-  fml::WeakPtr<GrContext> GetResourceContext() const;
+  fml::RefPtr<flutter::SkiaUnrefQueue> GetSkiaUnrefQueue() const;
 
   fml::WeakPtr<ImageDecoder> GetImageDecoder() const;