media/gpu/chromeos/VideoDecoderPipeline: refactor initialize logic

VideoDecoderPipeline holds together a (Vaapi|V4L2)VideoDecoder, a frame
pool and a converter. It gets a series of VideoDecoder create functions
from ChromeosVideoDecoderFactory, and needs to go through each decoder,
trying to create and then Initialize() each -- the first one that works
is good to go.

VideoDecoderPipeline retrieves such create functions and holds on to the
last |used_create_vd_func_| along such Create+Initialize cycles (to
avoid repeating a potentially broken one) and relies on the factory's
GetCreateDecoderFunctions() to return all such functions /except/ the
one passed as argument. This logic, aside from convoluted, is broken if
there were more than 2 such create functions. This CL simplifies all
that by keeping a list of |remaining_create_decoder_functions_| that are
tried and, if failed, discarded.

During the moves along the different initialization methods (see [1]),
a given Status is constructed and filled to indicate a potential
failure. Status [2] works in a non-intuitive way because it must be
constructed with a given StatusCode, which becomes its code(), but can
AddCause() to it -more StatusCodes- that are sadly, opaque. ToT uses a
kChromeOSVideoDecoderNoDecoders as start StatusCode, so any subsequent
errors e.g. kDecoderFailedCreation or kDecoderFailedInitialization are
thrown into the opaque causes. This CL changes this to start with a kOk,
and then collect the first meaningful error StatusCode.

Unittests added to hopefully clarify and identify the use cases.

[1] https://i.imgur.com/qH17CTJ.jpg (or https://imgur.com/a/anCJ2Ig)
[2] https://source.chromium.org/chromium/chromium/src/+/master:media/base/status.h;l=41

Bug: 1040291
Change-Id: I35889605850eb51e0dfe9308688c092d2b755edd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2259472
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Reviewed-by: Jao-ke Chin-Lee <jchinlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781964}

media/gpu/chromeos/BUILD.gn

@@ -149,6 +149,7 @@ source_set("unit_tests") {
     "mailbox_video_frame_converter_unittest.cc",
     "platform_video_frame_pool_unittest.cc",
     "platform_video_frame_utils_unittest.cc",
+    "video_decoder_pipeline_unittest.cc",
   ]
 }
 

media/gpu/chromeos/chromeos_video_decoder_factory.cc

@@ -26,10 +26,9 @@ namespace media {
 
 namespace {
 
-// Get a list of the available functions for creating VideoDecoder.
-base::queue<VideoDecoderPipeline::CreateVDFunc> GetCreateVDFunctions(
-    VideoDecoderPipeline::CreateVDFunc cur_create_vd_func) {
-  static constexpr VideoDecoderPipeline::CreateVDFunc kCreateVDFuncs[] = {
+// Gets a list of the available functions for creating VideoDecoders.
+VideoDecoderPipeline::CreateDecoderFunctions GetCreateDecoderFunctions() {
+  constexpr VideoDecoderPipeline::CreateDecoderFunction kCreateVDFuncs[] = {
 #if BUILDFLAG(USE_VAAPI)
     &VaapiVideoDecoder::Create,
 #endif  // BUILDFLAG(USE_VAAPI)
@@ -39,12 +38,8 @@ base::queue<VideoDecoderPipeline::CreateVDFunc> GetCreateVDFunctions(
 #endif  // BUILDFLAG(USE_V4L2_CODEC)
   };
 
-  base::queue<VideoDecoderPipeline::CreateVDFunc> ret;
-  for (const auto& func : kCreateVDFuncs) {
-    if (func != cur_create_vd_func)
-      ret.push(func);
-  }
-  return ret;
+  return VideoDecoderPipeline::CreateDecoderFunctions(
+      kCreateVDFuncs, kCreateVDFuncs + base::size(kCreateVDFuncs));
 }
 
 }  // namespace
@@ -79,7 +74,7 @@ std::unique_ptr<VideoDecoder> ChromeosVideoDecoderFactory::Create(
   return VideoDecoderPipeline::Create(
       std::move(client_task_runner), std::move(frame_pool),
       std::move(frame_converter), std::move(media_log),
-      base::BindRepeating(&GetCreateVDFunctions));
+      base::BindRepeating(&GetCreateDecoderFunctions));
 }
 
 }  // namespace media

media/gpu/chromeos/video_decoder_pipeline.cc

@@ -55,6 +55,14 @@ base::Optional<Fourcc> PickRenderableFourcc(
   return base::nullopt;
 }
 
+// Appends |new_status| to |parent_status| unless |parent_status| is kOk, in
+// that case we cannot append, just forward |new_status| then.
+Status AppendOrForwardStatus(Status parent_status, Status new_status) {
+  if (parent_status.is_ok())
+    return new_status;
+  return std::move(parent_status).AddCause(std::move(new_status));
+}
+
 }  //  namespace
 
 DecoderInterface::DecoderInterface(
@@ -70,34 +78,33 @@ std::unique_ptr<VideoDecoder> VideoDecoderPipeline::Create(
     std::unique_ptr<DmabufVideoFramePool> frame_pool,
     std::unique_ptr<VideoFrameConverter> frame_converter,
     std::unique_ptr<MediaLog> /*media_log*/,
-    GetCreateVDFunctionsCB get_create_vd_functions_cb) {
+    GetCreateDecoderFunctionsCB get_create_decoder_functions_cb) {
   if (!client_task_runner || !frame_pool || !frame_converter) {
     VLOGF(1) << "One of arguments is nullptr.";
     return nullptr;
   }
 
-  if (get_create_vd_functions_cb.Run(nullptr).empty()) {
+  if (get_create_decoder_functions_cb.Run().empty()) {
     VLOGF(1) << "No available function to create video decoder.";
     return nullptr;
   }
 
   return base::WrapUnique<VideoDecoder>(new VideoDecoderPipeline(
       std::move(client_task_runner), std::move(frame_pool),
-      std::move(frame_converter), std::move(get_create_vd_functions_cb)));
+      std::move(frame_converter), std::move(get_create_decoder_functions_cb)));
 }
 
 VideoDecoderPipeline::VideoDecoderPipeline(
     scoped_refptr<base::SequencedTaskRunner> client_task_runner,
     std::unique_ptr<DmabufVideoFramePool> frame_pool,
     std::unique_ptr<VideoFrameConverter> frame_converter,
-    GetCreateVDFunctionsCB get_create_vd_functions_cb)
+    GetCreateDecoderFunctionsCB get_create_decoder_functions_cb)
     : client_task_runner_(std::move(client_task_runner)),
       decoder_task_runner_(base::ThreadPool::CreateSingleThreadTaskRunner(
           {base::WithBaseSyncPrimitives(), base::TaskPriority::USER_VISIBLE},
           base::SingleThreadTaskRunnerThreadMode::DEDICATED)),
       main_frame_pool_(std::move(frame_pool)),
-      frame_converter_(std::move(frame_converter)),
-      get_create_vd_functions_cb_(std::move(get_create_vd_functions_cb)) {
+      frame_converter_(std::move(frame_converter)) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(client_sequence_checker_);
   DETACH_FROM_SEQUENCE(decoder_sequence_checker_);
   DCHECK(main_frame_pool_);
@@ -108,6 +115,8 @@ VideoDecoderPipeline::VideoDecoderPipeline(
   client_weak_this_ = client_weak_this_factory_.GetWeakPtr();
   decoder_weak_this_ = decoder_weak_this_factory_.GetWeakPtr();
 
+  remaining_create_decoder_functions_ = get_create_decoder_functions_cb.Run();
+
   main_frame_pool_->set_parent_task_runner(decoder_task_runner_);
   frame_converter_->Initialize(
       decoder_task_runner_,
@@ -144,7 +153,7 @@ void VideoDecoderPipeline::DestroyTask() {
   frame_converter_.reset();
 
   decoder_.reset();
-  used_create_vd_func_ = nullptr;
+  remaining_create_decoder_functions_.clear();
 
   delete this;
 }
@@ -215,71 +224,68 @@ void VideoDecoderPipeline::Initialize(const VideoDecoderConfig& config,
 void VideoDecoderPipeline::InitializeTask(const VideoDecoderConfig& config,
                                           InitCB init_cb,
                                           const OutputCB& output_cb) {
+  DVLOGF(3);
   DCHECK_CALLED_ON_VALID_SEQUENCE(decoder_sequence_checker_);
   DCHECK(!init_cb_);
 
   client_output_cb_ = std::move(output_cb);
   init_cb_ = std::move(init_cb);
-  base::queue<VideoDecoderPipeline::CreateVDFunc> create_vd_funcs =
-      get_create_vd_functions_cb_.Run(used_create_vd_func_);
 
+  // Initialize() and correspondingly InitializeTask(), are called both on first
+  // initialization and on subsequent stream |config| changes, e.g. change of
+  // resolution. Subsequent initializations are marked by |decoder_| already
+  // existing.
   if (!decoder_) {
-    CreateAndInitializeVD(std::move(create_vd_funcs), config,
-                          StatusCode::kChromeOSVideoDecoderNoDecoders);
+    CreateAndInitializeVD(config, Status());
   } else {
     decoder_->Initialize(
         config,
-        // If it fails to re-initialize current |decoder_|, it will create
-        // another decoder instance by trying available VD creation functions
-        // again. See |OnInitializeDone| for detail.
         base::BindOnce(&VideoDecoderPipeline::OnInitializeDone,
-                       decoder_weak_this_, std::move(create_vd_funcs), config,
-                       StatusCode::kChromeOSVideoDecoderNoDecoders),
+                       decoder_weak_this_, config, Status()),
         base::BindRepeating(&VideoDecoderPipeline::OnFrameDecoded,
                             decoder_weak_this_));
   }
 }
 
-void VideoDecoderPipeline::CreateAndInitializeVD(
-    base::queue<VideoDecoderPipeline::CreateVDFunc> create_vd_funcs,
-    VideoDecoderConfig config,
+void VideoDecoderPipeline::CreateAndInitializeVD(VideoDecoderConfig config,
                                                  Status parent_error) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(decoder_sequence_checker_);
   DCHECK(init_cb_);
   DCHECK(!decoder_);
-  DCHECK(!used_create_vd_func_);
   DVLOGF(3);
 
-  if (create_vd_funcs.empty()) {
-    DVLOGF(2) << "No available video decoder.";
+  if (remaining_create_decoder_functions_.empty()) {
+    DVLOGF(2) << "No remaining video decoder create functions to try";
     client_task_runner_->PostTask(
-        FROM_HERE, base::BindOnce(std::move(init_cb_), parent_error));
+        FROM_HERE,
+        base::BindOnce(
+            std::move(init_cb_),
+            AppendOrForwardStatus(
+                parent_error, StatusCode::kChromeOSVideoDecoderNoDecoders)));
     return;
   }
 
-  used_create_vd_func_ = create_vd_funcs.front();
-  create_vd_funcs.pop();
-  decoder_ = used_create_vd_func_(decoder_task_runner_, decoder_weak_this_);
+  decoder_ = remaining_create_decoder_functions_.front()(decoder_task_runner_,
+                                                         decoder_weak_this_);
+  remaining_create_decoder_functions_.pop_front();
+
   if (!decoder_) {
-    DVLOGF(2) << "Failed to create VideoDecoder.";
-    used_create_vd_func_ = nullptr;
+    DVLOGF(2) << "|decoder_| creation failed, trying again with the next "
+                 "available create function.";
     return CreateAndInitializeVD(
-        std::move(create_vd_funcs), config,
-        std::move(parent_error).AddCause(StatusCode::kDecoderFailedCreation));
+        config, AppendOrForwardStatus(parent_error,
+                                      StatusCode::kDecoderFailedCreation));
   }
 
   decoder_->Initialize(
       config,
       base::BindOnce(&VideoDecoderPipeline::OnInitializeDone,
-                     decoder_weak_this_, std::move(create_vd_funcs), config,
-                     std::move(parent_error)),
+                     decoder_weak_this_, config, std::move(parent_error)),
       base::BindRepeating(&VideoDecoderPipeline::OnFrameDecoded,
                           decoder_weak_this_));
 }
 
-void VideoDecoderPipeline::OnInitializeDone(
-    base::queue<VideoDecoderPipeline::CreateVDFunc> create_vd_funcs,
-    VideoDecoderConfig config,
+void VideoDecoderPipeline::OnInitializeDone(VideoDecoderConfig config,
                                             Status parent_error,
                                             Status status) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(decoder_sequence_checker_);
@@ -287,7 +293,7 @@ void VideoDecoderPipeline::OnInitializeDone(
   DVLOGF(4) << "Initialization status = " << status.code();
 
   if (status.is_ok()) {
-    DVLOGF(2) << "Initialize VD successfully.";
+    DVLOGF(2) << "|decoder_| successfully initialized.";
     // TODO(tmathmeyer) consider logging the causes of |parent_error| as they
     // might have infor about why other decoders failed.
     client_task_runner_->PostTask(
@@ -295,11 +301,11 @@ void VideoDecoderPipeline::OnInitializeDone(
     return;
   }
 
-  DVLOGF(3) << "Reset VD, try the next create function.";
+  DVLOGF(3) << "|decoder_| initialization failed, trying again with the next "
+               "available create function.";
   decoder_ = nullptr;
-  used_create_vd_func_ = nullptr;
-  CreateAndInitializeVD(std::move(create_vd_funcs), config,
-                        std::move(parent_error).AddCause(std::move(status)));
+  CreateAndInitializeVD(config,
+                        AppendOrForwardStatus(parent_error, std::move(status)));
 }
 
 void VideoDecoderPipeline::Reset(base::OnceClosure closure) {

media/gpu/chromeos/video_decoder_pipeline.h

@@ -8,7 +8,6 @@
 #include <memory>
 
 #include "base/callback_forward.h"
-#include "base/containers/queue.h"
 #include "base/memory/weak_ptr.h"
 #include "base/optional.h"
 #include "base/sequence_checker.h"
@@ -127,19 +126,19 @@ class MEDIA_GPU_EXPORT DecoderInterface {
 class MEDIA_GPU_EXPORT VideoDecoderPipeline : public VideoDecoder,
                                               public DecoderInterface::Client {
  public:
-  // Function signature for creating VideoDecoder.
-  using CreateVDFunc = std::unique_ptr<DecoderInterface> (*)(
+  using CreateDecoderFunction = std::unique_ptr<DecoderInterface> (*)(
       scoped_refptr<base::SequencedTaskRunner>,
       base::WeakPtr<DecoderInterface::Client>);
-  using GetCreateVDFunctionsCB =
-      base::RepeatingCallback<base::queue<CreateVDFunc>(CreateVDFunc)>;
+  using CreateDecoderFunctions = std::list<CreateDecoderFunction>;
+  using GetCreateDecoderFunctionsCB =
+      base::RepeatingCallback<CreateDecoderFunctions()>;
 
   static std::unique_ptr<VideoDecoder> Create(
       scoped_refptr<base::SequencedTaskRunner> client_task_runner,
       std::unique_ptr<DmabufVideoFramePool> frame_pool,
       std::unique_ptr<VideoFrameConverter> frame_converter,
       std::unique_ptr<MediaLog> media_log,
-      GetCreateVDFunctionsCB get_create_vd_functions_cb);
+      GetCreateDecoderFunctionsCB get_create_decoder_functions_cb);
 
   ~VideoDecoderPipeline() override;
 
@@ -169,11 +168,13 @@ class MEDIA_GPU_EXPORT VideoDecoderPipeline : public VideoDecoder,
       const gfx::Rect& visible_rect) override;
 
  private:
+  friend class VideoDecoderPipelineTest;
+
   VideoDecoderPipeline(
       scoped_refptr<base::SequencedTaskRunner> client_task_runner,
       std::unique_ptr<DmabufVideoFramePool> frame_pool,
       std::unique_ptr<VideoFrameConverter> frame_converter,
-      GetCreateVDFunctionsCB get_create_vd_functions_cb);
+      GetCreateDecoderFunctionsCB get_create_decoder_functions_cb);
   void Destroy() override;
   void DestroyTask();
 
@@ -183,13 +184,10 @@ class MEDIA_GPU_EXPORT VideoDecoderPipeline : public VideoDecoder,
   void ResetTask(base::OnceClosure closure);
   void DecodeTask(scoped_refptr<DecoderBuffer> buffer, DecodeCB decode_cb);
 
-  void CreateAndInitializeVD(base::queue<CreateVDFunc> create_vd_funcs,
-                             VideoDecoderConfig config,
-                             Status parent_error);
-  void OnInitializeDone(base::queue<CreateVDFunc> create_vd_funcs,
-                        VideoDecoderConfig config,
+  void CreateAndInitializeVD(VideoDecoderConfig config, Status parent_error);
+  void OnInitializeDone(VideoDecoderConfig config,
                         Status parent_error,
-                        Status success);
+                        Status status);
 
   void OnDecodeDone(bool eos_buffer, DecodeCB decode_cb, DecodeStatus status);
   void OnResetDone();
@@ -240,14 +238,14 @@ class MEDIA_GPU_EXPORT VideoDecoderPipeline : public VideoDecoder,
   // |client_task_runner_|.
   std::unique_ptr<VideoFrameConverter> frame_converter_;
 
-  // The callback to get a list of function for creating DecoderInterface.
-  GetCreateVDFunctionsCB get_create_vd_functions_cb_;
-
   // The current video decoder implementation. Valid after initialization is
   // successfully done.
   std::unique_ptr<DecoderInterface> decoder_;
-  // The create function of |decoder_|. nullptr iff |decoder_| is nullptr.
-  CreateVDFunc used_create_vd_func_ = nullptr;
+
+  // |remaining_create_decoder_functions_| holds all the potential video decoder
+  // creation functions. We try them all in the given order until one succeeds.
+  // Only used after initialization on |decoder_sequence_checker_|.
+  CreateDecoderFunctions remaining_create_decoder_functions_;
 
   // Callback from the client. These callback are called on
   // |client_task_runner_|.

media/gpu/chromeos/video_decoder_pipeline_unittest.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/gpu/chromeos/video_decoder_pipeline.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/test/gmock_callback_support.h"
+#include "base/test/task_environment.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "media/base/media_util.h"
+#include "media/base/status.h"
+#include "media/base/video_decoder_config.h"
+#include "media/gpu/chromeos/dmabuf_video_frame_pool.h"
+#include "media/gpu/chromeos/mailbox_video_frame_converter.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using base::test::RunClosure;
+using ::testing::_;
+using ::testing::TestWithParam;
+
+namespace media {
+
+MATCHER_P(MatchesStatusCode, status_code, "") {
+  // media::Status doesn't provide an operator==(...), we add here a simple one.
+  return arg.code() == status_code;
+}
+
+class MockVideoFramePool : public DmabufVideoFramePool {
+ public:
+  MockVideoFramePool() = default;
+  ~MockVideoFramePool() override = default;
+
+  // DmabufVideoFramePool implementation.
+  MOCK_METHOD5(Initialize,
+               base::Optional<GpuBufferLayout>(const Fourcc&,
+                                               const gfx::Size&,
+                                               const gfx::Rect&,
+                                               const gfx::Size&,
+                                               size_t));
+  MOCK_METHOD0(GetFrame, scoped_refptr<VideoFrame>());
+  MOCK_METHOD0(IsExhausted, bool());
+  MOCK_METHOD1(NotifyWhenFrameAvailable, void(base::OnceClosure));
+};
+
+constexpr gfx::Size kCodedSize(48, 36);
+
+class MockDecoder : public DecoderInterface {
+ public:
+  MockDecoder()
+      : DecoderInterface(base::ThreadTaskRunnerHandle::Get(),
+                         base::WeakPtr<DecoderInterface::Client>(nullptr)) {}
+  ~MockDecoder() override = default;
+
+  MOCK_METHOD3(Initialize,
+               void(const VideoDecoderConfig&, InitCB, const OutputCB&));
+  MOCK_METHOD2(Decode, void(scoped_refptr<DecoderBuffer>, DecodeCB));
+  MOCK_METHOD1(Reset, void(base::OnceClosure));
+  MOCK_METHOD0(ApplyResolutionChange, void());
+};
+
+struct DecoderPipelineTestParams {
+  VideoDecoderPipeline::CreateDecoderFunctions create_decoder_functions;
+  StatusCode status_code;
+};
+
+class VideoDecoderPipelineTest
+    : public testing::TestWithParam<DecoderPipelineTestParams> {
+ public:
+  VideoDecoderPipelineTest()
+      : config_(kCodecVP8,
+                VP8PROFILE_ANY,
+                VideoDecoderConfig::AlphaMode::kIsOpaque,
+                VideoColorSpace(),
+                kNoTransformation,
+                kCodedSize,
+                gfx::Rect(kCodedSize),
+                kCodedSize,
+                EmptyExtraData(),
+                EncryptionScheme::kUnencrypted),
+        pool_(new MockVideoFramePool),
+        converter_(new VideoFrameConverter),
+        decoder_(new VideoDecoderPipeline(
+            base::ThreadTaskRunnerHandle::Get(),
+            std::move(pool_),
+            std::move(converter_),
+            base::BindRepeating([]() {
+              // This callback needs to be configured in the individual tests.
+              return VideoDecoderPipeline::CreateDecoderFunctions();
+            }))) {}
+  ~VideoDecoderPipelineTest() override = default;
+
+  void TearDown() override {
+    decoder_.release()->Destroy();
+    task_environment_.RunUntilIdle();
+  }
+  MOCK_METHOD1(OnInit, void(Status));
+  MOCK_METHOD1(OnOutput, void(scoped_refptr<VideoFrame>));
+
+  void SetCreateDecoderFunctions(
+      VideoDecoderPipeline::CreateDecoderFunctions functions) {
+    decoder_->remaining_create_decoder_functions_ = functions;
+  }
+
+  void InitializeDecoder() {
+    decoder_->Initialize(
+        config_, false /* low_delay */, nullptr /* cdm_context */,
+        base::BindOnce(&VideoDecoderPipelineTest::OnInit,
+                       base::Unretained(this)),
+        base::BindRepeating(&VideoDecoderPipelineTest::OnOutput,
+                            base::Unretained(this)),
+        base::DoNothing());
+  }
+
+  static std::unique_ptr<DecoderInterface> CreateNullMockDecoder(
+      scoped_refptr<base::SequencedTaskRunner> /* decoder_task_runner */,
+      base::WeakPtr<DecoderInterface::Client> /* client */) {
+    return nullptr;
+  }
+
+  // Creates a MockDecoder with an EXPECT_CALL on Initialize that returns ok.
+  static std::unique_ptr<DecoderInterface> CreateGoodMockDecoder(
+      scoped_refptr<base::SequencedTaskRunner> /* decoder_task_runner */,
+      base::WeakPtr<DecoderInterface::Client> /* client */) {
+    std::unique_ptr<MockDecoder> decoder(new MockDecoder());
+    EXPECT_CALL(*decoder, Initialize(_, _, _))
+        .WillOnce(::testing::WithArgs<1>([](VideoDecoder::InitCB init_cb) {
+          std::move(init_cb).Run(OkStatus());
+        }));
+    return std::move(decoder);
+  }
+
+  // Creates a MockDecoder with an EXPECT_CALL on Initialize that returns error.
+  static std::unique_ptr<DecoderInterface> CreateBadMockDecoder(
+      scoped_refptr<base::SequencedTaskRunner> /* decoder_task_runner */,
+      base::WeakPtr<DecoderInterface::Client> /* client */) {
+    std::unique_ptr<MockDecoder> decoder(new MockDecoder());
+    EXPECT_CALL(*decoder, Initialize(_, _, _))
+        .WillOnce(::testing::WithArgs<1>([](VideoDecoder::InitCB init_cb) {
+          std::move(init_cb).Run(StatusCode::kDecoderFailedInitialization);
+        }));
+    return std::move(decoder);
+  }
+
+  DecoderInterface* GetUnderlyingDecoder() { return decoder_->decoder_.get(); }
+
+  base::test::TaskEnvironment task_environment_;
+  const VideoDecoderConfig config_;
+  DecoderInterface* underlying_decoder_ptr_ = nullptr;
+
+  std::unique_ptr<MockVideoFramePool> pool_;
+  std::unique_ptr<VideoFrameConverter> converter_;
+  std::unique_ptr<VideoDecoderPipeline> decoder_;
+};
+
+// Verifies the status code for several typical CreateDecoderFunctions cases.
+TEST_P(VideoDecoderPipelineTest, Initialize) {
+  SetCreateDecoderFunctions(GetParam().create_decoder_functions);
+
+  base::RunLoop run_loop;
+  base::Closure quit_closure = run_loop.QuitClosure();
+  EXPECT_CALL(*this, OnInit(MatchesStatusCode(GetParam().status_code)))
+      .WillOnce(RunClosure(quit_closure));
+
+  InitializeDecoder();
+  run_loop.Run();
+
+  EXPECT_EQ(GetParam().status_code == StatusCode::kOk,
+            !!GetUnderlyingDecoder());
+}
+
+const struct DecoderPipelineTestParams kDecoderPipelineTestParams[] = {
+    // An empty set of CreateDecoderFunctions.
+    {{}, StatusCode::kChromeOSVideoDecoderNoDecoders},
+
+    // Just one CreateDecoderFunctions that fails to Create() (i.e. returns a
+    // null Decoder)
+    {{&VideoDecoderPipelineTest::CreateNullMockDecoder},
+     StatusCode::kDecoderFailedCreation},
+
+    // Just one CreateDecoderFunctions that works fine, i.e. Create()s and
+    // Initialize()s correctly.
+    {{&VideoDecoderPipelineTest::CreateGoodMockDecoder}, StatusCode::kOk},
+
+    // One CreateDecoderFunctions that Create()s ok but fails to Initialize()
+    // correctly
+    {{&VideoDecoderPipelineTest::CreateBadMockDecoder},
+     StatusCode::kDecoderFailedInitialization},
+
+    // Two CreateDecoderFunctions, one that fails to Create() (i.e. returns a
+    // null Decoder), and one that works. The first error StatusCode is lost
+    // because VideoDecoderPipeline::OnInitializeDone() throws it away.
+    {{&VideoDecoderPipelineTest::CreateNullMockDecoder,
+      &VideoDecoderPipelineTest::CreateGoodMockDecoder},
+     StatusCode::kOk},
+
+    // Two CreateDecoderFunctions, one that Create()s ok but fails  to
+    // Initialize(), and one that works. The first error StatusCode is lost
+    // because VideoDecoderPipeline::OnInitializeDone() throws it away.
+    {{&VideoDecoderPipelineTest::CreateBadMockDecoder,
+      &VideoDecoderPipelineTest::CreateGoodMockDecoder},
+     StatusCode::kOk},
+
+    // Two CreateDecoderFunctions, one that fails to Create() (i.e. returns a
+    // null Decoder), and one that fails to Initialize(). The first error
+    // StatusCode is the only one we can check here: a Status object is created
+    // with a "primary" StatusCode, archiving subsequent ones in a private
+    // member.
+    {{&VideoDecoderPipelineTest::CreateNullMockDecoder,
+      &VideoDecoderPipelineTest::CreateBadMockDecoder},
+     StatusCode::kDecoderFailedCreation},
+    // Previous one in reverse order.
+    {{&VideoDecoderPipelineTest::CreateBadMockDecoder,
+      &VideoDecoderPipelineTest::CreateNullMockDecoder},
+     StatusCode::kDecoderFailedInitialization},
+
+    {{&VideoDecoderPipelineTest::CreateBadMockDecoder,
+      &VideoDecoderPipelineTest::CreateBadMockDecoder,
+      &VideoDecoderPipelineTest::CreateGoodMockDecoder},
+     StatusCode::kOk},
+};
+
+INSTANTIATE_TEST_SUITE_P(All,
+                         VideoDecoderPipelineTest,
+                         testing::ValuesIn(kDecoderPipelineTestParams));
+
+}  // namespace media