[webcodecs] Various DecoderTemplate shutdown cleanups

1. Use DeleteSoon() when destroying the |decoder_| to avoid destructing
   in error conditions where it's callback (OnDecodeDone()) is actively
   executing.

2. Call Shutdown() from ContextDestroyed() to invoke full reset
   algorithm and tidily clean up all state.

Bug: 1267426
Change-Id: I927d8a3bd245b3f833e73c74103cbaacf6d73406
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3277273
Commit-Queue: Chrome Cunningham <chcunningham@chromium.org>
Auto-Submit: Chrome Cunningham <chcunningham@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Cr-Commit-Position: refs/heads/main@{#941390}

third_party/blink/renderer/modules/webcodecs/decoder_template.cc

@@ -79,8 +79,10 @@ DecoderTemplate<Traits>::DecoderTemplate(ScriptState* script_state,
   ExecutionContext* context = GetExecutionContext();
   DCHECK(context);
 
-  logger_ = std::make_unique<CodecLogger>(
-      context, context->GetTaskRunner(TaskType::kInternalMedia));
+  main_thread_task_runner_ =
+      context->GetTaskRunner(TaskType::kInternalMediaRealTime);
+
+  logger_ = std::make_unique<CodecLogger>(context, main_thread_task_runner_);
 
   logger_->log()->SetProperty<media::MediaLogProperty::kFrameUrl>(
       context->Url().GetString().Ascii());
@@ -506,8 +508,10 @@ void DecoderTemplate<Traits>::Shutdown(DOMException* exception) {
   // Prevent any further logging from being reported.
   logger_->Neuter();
 
-  // Clear decoding and JS-visible queue state.
-  decoder_.reset();
+  // Clear decoding and JS-visible queue state. Use DeleteSoon() to avoid
+  // deleting decoder_ when its callback (e.g. OnDecodeDone()) may be below us
+  // in the stack.
+  main_thread_task_runner_->DeleteSoon(FROM_HERE, std::move(decoder_));
 
   if (pending_request_) {
     // This request was added as part of calling ResetAlgorithm above. However,
@@ -724,9 +728,8 @@ void DecoderTemplate<Traits>::TraceQueueSizes() const {
 
 template <typename Traits>
 void DecoderTemplate<Traits>::ContextDestroyed() {
-  state_ = V8CodecState(V8CodecState::Enum::kClosed);
-  logger_->Neuter();
-  decoder_.reset();
+  // Deallocate resources and supress late callbacks from media thread.
+  Shutdown();
 }
 
 template <typename Traits>

third_party/blink/renderer/modules/webcodecs/decoder_template.h

@@ -29,6 +29,10 @@
 #include "third_party/blink/renderer/platform/heap/heap_allocator.h"
 #include "third_party/blink/renderer/platform/heap/member.h"
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace media {
 class GpuVideoAcceleratorFactories;
 class ScopedDecodeTrace;
@@ -227,6 +231,9 @@ class MODULES_EXPORT DecoderTemplate
 
   // Keyframes are required after configure(), flush(), and reset().
   bool require_key_frame_ = true;
+
+  // Task runner for main thread.
+  scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
 };
 
 }  // namespace blink

third_party/blink/renderer/modules/webcodecs/decoder_template_test.cc

@@ -215,9 +215,6 @@ TYPED_TEST(DecoderTemplateTest, MAYBE_CodecReclamation) {
   testing::Mock::VerifyAndClearExpectations(error_callback);
 }
 
-// Note: AudioDecoder and VideoDecoder specific tests should be put in
-// audio_decoder_test.cc and video_decoder_test.cc respectively.
-
 }  // namespace
 
 }  // namespace blink