Introduce AudioIPCFactory.

content/renderer/media/audio_ipc_factory.cc

+// Copyright 2017 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 "content/renderer/media/audio_ipc_factory.h"
+
+#include <utility>
+
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "base/single_thread_task_runner.h"
+#include "content/renderer/media/audio_message_filter.h"
+#include "content/renderer/media/mojo_audio_output_ipc.h"
+#include "services/service_manager/public/cpp/interface_provider.h"
+
+namespace content {
+
+AudioIPCFactory* AudioIPCFactory::instance_ = nullptr;
+
+AudioIPCFactory::AudioIPCFactory(
+    const scoped_refptr<AudioMessageFilter>& audio_message_filter,
+    const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner)
+    : audio_message_filter_(audio_message_filter),
+      io_task_runner_(io_task_runner) {
+  // TODO(maxmorin): In the future, use a feature to control whether
+  // audio_message_filter should be used.
+  DCHECK(!instance_);
+  instance_ = this;
+}
+
+AudioIPCFactory::~AudioIPCFactory() {
+  // Allow destruction in tests.
+  DCHECK_EQ(instance_, this);
+  instance_ = nullptr;
+}
+
+std::unique_ptr<media::AudioOutputIPC> AudioIPCFactory::CreateAudioOutputIPC(
+    int frame_id) const {
+  if (UsingMojoFactories()) {
+    // Unretained is safe due to the contract at the top of the header file.
+    return base::MakeUnique<MojoAudioOutputIPC>(base::BindRepeating(
+        &AudioIPCFactory::GetRemoteFactory, base::Unretained(this), frame_id));
+  }
+  return audio_message_filter_->CreateAudioOutputIPC(frame_id);
+}
+
+void AudioIPCFactory::MaybeRegisterRemoteFactory(
+    int frame_id,
+    service_manager::InterfaceProvider* interface_provider) {
+  if (!UsingMojoFactories())
+    return;
+  mojom::RendererAudioOutputStreamFactoryPtr factory_ptr;
+  interface_provider->GetInterface(&factory_ptr);
+  // PassInterface unbinds the message pipe from the current thread. This
+  // allows us to bind it to the IO thread.
+  // Unretained is safe due to the contract at the top of the header file.
+  io_task_runner_->PostTask(
+      FROM_HERE,
+      base::BindOnce(&AudioIPCFactory::RegisterRemoteFactoryOnIOThread,
+                     base::Unretained(this), frame_id,
+                     factory_ptr.PassInterface()));
+}
+
+void AudioIPCFactory::MaybeDeregisterRemoteFactory(int frame_id) {
+  if (!UsingMojoFactories())
+    return;
+  if (!io_task_runner_->BelongsToCurrentThread()) {

[DaleCurtis, 2017/05/31 20:48:09]

Since MaybeRegisterRemoteFactory() doesn't add the frame_id to factory_ptrs, it
seems you may never remove it if register / deregister happen back to back? Add
a unittest for this case too.

[Max Morin, 2017/06/01 13:58:42]

Hmm, this is only called from the main thread in practice, so it's safe because
of that. On the other hand, adding such conditions to the API isn't ideal, so
I'll change this to always post, and move the erase call to a separate function.
This will ensure that tasks are executed on the IO thread in the order we expect
them to. Also added test.

+    // Unretained is safe due to the contract at the top of the header file.
+    io_task_runner_->PostTask(
+        FROM_HERE,
+        base::BindOnce(&AudioIPCFactory::MaybeDeregisterRemoteFactory,
+                       base::Unretained(this), frame_id));
+    return;
+  }
+  factory_ptrs_.erase(frame_id);
+}
+
+mojom::RendererAudioOutputStreamFactory* AudioIPCFactory::GetRemoteFactory(
+    int frame_id) const {
+  DCHECK(io_task_runner_->BelongsToCurrentThread());
+  DCHECK(UsingMojoFactories());
+  auto it = factory_ptrs_.find(frame_id);
+  return it == factory_ptrs_.end() ? nullptr : it->second.get();
+}
+
+void AudioIPCFactory::RegisterRemoteFactoryOnIOThread(
+    int frame_id,
+    mojom::RendererAudioOutputStreamFactoryPtrInfo factory_ptr_info) {
+  DCHECK(io_task_runner_->BelongsToCurrentThread());
+  DCHECK(UsingMojoFactories());
+  std::pair<StreamFactoryMap::iterator, bool> emplace_result =
+      factory_ptrs_.emplace(frame_id,
+                            mojo::MakeProxy(std::move(factory_ptr_info)));
+
+  DCHECK(emplace_result.second) << "Attempt to register a factory for a "
+                                   "frame which already has a factory "
+                                   "registered.";
+
+  auto& emplaced_factory = emplace_result.first->second;
+  DCHECK(emplaced_factory.is_bound())
+      << "Factory is not bound to a remote implementation.";
+
+  // Unretained is safe because |this| owns the binding, so a connection error
+  // cannot trigger after destruction.
+  emplaced_factory.set_connection_error_handler(
+      base::Bind(&AudioIPCFactory::MaybeDeregisterRemoteFactory,
+                 base::Unretained(this), frame_id));
+}
+
+bool AudioIPCFactory::UsingMojoFactories() const {
+  return audio_message_filter_ == nullptr;
+}
+
+}  // namespace content