Move GpuMediaService to gpu main thread on Windows.

Since the CDM runs on the main thread, and we can't decode on a
separate thread anyway, just start the whole GpuMediaService on
the GPU main thread.

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I69e41919f96348c86289844231fe2506822a0ebd
Reviewed-on: https://chromium-review.googlesource.com/1112593
Commit-Queue: Frank Liberato <liberato@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570242}

content/gpu/gpu_service_factory.cc

@@ -8,6 +8,7 @@
 
 #include "base/task_scheduler/post_task.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "build/build_config.h"
 #include "services/shape_detection/public/mojom/constants.mojom.h"
 #include "services/shape_detection/shape_detection_service.h"
 
@@ -54,9 +55,14 @@ void GpuServiceFactory::RegisterServices(ServiceMap* services) {
   // This service will host audio/video decoders, and if these decoding
   // operations are blocked, user may hear audio glitch or see video freezing,
   // hence "user blocking".
+#if defined(OS_WIN)
+  // Run everything on the gpu main thread, since that's where the CDM runs.
+  info.task_runner = task_runner_;
+#else
   // TODO(crbug.com/786169): Check whether this needs to be single threaded.
   info.task_runner = base::CreateSingleThreadTaskRunnerWithTraits(
       {base::TaskPriority::USER_BLOCKING});
+#endif  // defined(OS_WIN)
   services->insert(std::make_pair("media", info));
 #endif  // BUILDFLAG(ENABLE_MOJO_MEDIA_IN_GPU_PROCESS)
 

media/gpu/windows/d3d11_video_decoder.cc

@@ -80,7 +80,10 @@ D3D11VideoDecoder::~D3D11VideoDecoder() {
   // Post destruction to the main thread.  When this executes, it will also
   // cancel pending callbacks into |impl_| via |impl_weak_|.  Callbacks out
   // from |impl_| will be cancelled by |weak_factory_| when we return.
-  impl_task_runner_->DeleteSoon(FROM_HERE, std::move(impl_));
+  if (impl_task_runner_->RunsTasksInCurrentSequence())
+    impl_.reset();
+  else
+    impl_task_runner_->DeleteSoon(FROM_HERE, std::move(impl_));
 }
 
 std::string D3D11VideoDecoder::GetDisplayName() const {
@@ -100,8 +103,14 @@ void D3D11VideoDecoder::Initialize(
     return;
   }
 
-  // Bind our own init / output cb that hop to this thread, so we don't call the
-  // originals on some other thread.
+  if (impl_task_runner_->RunsTasksInCurrentSequence()) {
+    impl_->Initialize(config, low_delay, cdm_context, init_cb, output_cb,
+                      waiting_for_decryption_key_cb);
+    return;
+  }
+
+  // Bind our own init / output cb that hop to this thread, so we don't call
+  // the originals on some other thread.
   // Important but subtle note: base::Bind will copy |config_| since it's a
   // const ref.
   // TODO(liberato): what's the lifetime of |cdm_context|?
@@ -117,6 +126,11 @@ void D3D11VideoDecoder::Initialize(
 
 void D3D11VideoDecoder::Decode(scoped_refptr<DecoderBuffer> buffer,
                                const DecodeCB& decode_cb) {
+  if (impl_task_runner_->RunsTasksInCurrentSequence()) {
+    impl_->Decode(std::move(buffer), decode_cb);
+    return;
+  }
+
   impl_task_runner_->PostTask(
       FROM_HERE,
       base::BindOnce(
@@ -125,6 +139,11 @@ void D3D11VideoDecoder::Decode(scoped_refptr<DecoderBuffer> buffer,
 }
 
 void D3D11VideoDecoder::Reset(const base::Closure& closure) {
+  if (impl_task_runner_->RunsTasksInCurrentSequence()) {
+    impl_->Reset(closure);
+    return;
+  }
+
   impl_task_runner_->PostTask(
       FROM_HERE, base::BindOnce(&VideoDecoder::Reset, impl_weak_,
                                 BindToCurrentThreadIfWeakPtr(