From 783558767f4b55eca6638a9d5319be52810ea532 Mon Sep 17 00:00:00 2001
From: Matej Knopp <matej.knopp@gmail.com>
Date: Thu, 13 May 2021 12:47:15 +0200
Subject: [PATCH 1/2] Remove layer trees from pipeline when destroying Animator

Fixes https://github.com/flutter/flutter/issues/82353
---
 shell/common/animator.cc |  5 ++++-
 shell/common/pipeline.h  | 12 ++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/shell/common/animator.cc b/shell/common/animator.cc
index 2fbd6fa772f1e..8ba822fb938b8 100644
--- a/shell/common/animator.cc
+++ b/shell/common/animator.cc
@@ -49,7 +49,10 @@ Animator::Animator(Delegate& delegate,
       weak_factory_(this) {
 }
 
-Animator::~Animator() = default;
+Animator::~Animator() {
+  // Remove all queued layer trees to ensure that Skia objects are unreffed.
+  layer_tree_pipeline_->Clear();
+}
 
 void Animator::Stop() {
   paused_ = true;
diff --git a/shell/common/pipeline.h b/shell/common/pipeline.h
index d05e0f50612c0..310ebb1d0c50c 100644
--- a/shell/common/pipeline.h
+++ b/shell/common/pipeline.h
@@ -151,6 +151,12 @@ class Pipeline : public fml::RefCountedThreadSafe<Pipeline<R>> {
 
     {
       std::scoped_lock lock(queue_mutex_);
+
+      if (queue_.empty()) {
+        // Items were removed from queue in Clear after available_ was
+        // signalled.
+        return PipelineConsumeResult::NoneAvailable;
+      }
       std::tie(resource, trace_id) = std::move(queue_.front());
       queue_.pop_front();
       items_count = queue_.size();
@@ -171,6 +177,12 @@ class Pipeline : public fml::RefCountedThreadSafe<Pipeline<R>> {
                            : PipelineConsumeResult::Done;
   }
 
+  /// Remove all items from the queue.
+  void Clear() {
+    std::scoped_lock lock(queue_mutex_);
+    queue_.clear();
+  }
+
  private:
   const uint32_t depth_;
   fml::Semaphore empty_;

From 1c149366b43c28b75f83eb81b4720b4f72694e88 Mon Sep 17 00:00:00 2001
From: Matej Knopp <matej.knopp@gmail.com>
Date: Sun, 16 May 2021 18:19:59 +0200
Subject: [PATCH 2/2] Do not assert should_resubmit_frame after DestroyShell is
 called

---
 shell/common/shell_unittests.cc | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/shell/common/shell_unittests.cc b/shell/common/shell_unittests.cc
index 4c5090f34d8f0..18cd9f2a83367 100644
--- a/shell/common/shell_unittests.cc
+++ b/shell/common/shell_unittests.cc
@@ -701,9 +701,12 @@ TEST_F(ShellTest,
   auto end_frame_callback =
       [&](bool should_resubmit_frame,
           fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger) {
-        ASSERT_TRUE(raster_thread_merger.get() != nullptr);
-        ASSERT_TRUE(should_resubmit_frame);
-        end_frame_called = true;
+        // The asserts below are only valid until DestroyShell is called
+        if (!end_frame_called) {
+          ASSERT_TRUE(raster_thread_merger.get() != nullptr);
+          ASSERT_TRUE(should_resubmit_frame);
+          end_frame_called = true;
+        }
         end_frame_latch.Signal();
       };
   auto external_view_embedder = std::make_shared<ShellTestExternalViewEmbedder>(