Web MIDI: add an unit test to check MidiManager instantiation

media/midi/midi_manager.cc

 // Copyright (c) 2013 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/midi/midi_manager.h"
 
+#include "base/bind.h"
 #include "base/debug/trace_event.h"
+#include "base/message_loop/message_loop.h"
+#include "base/message_loop/message_loop_proxy.h"
 
 namespace media {
 
 #if !defined(OS_MACOSX) && !defined(OS_WIN) && !defined(USE_ALSA) && \
     !defined(OS_ANDROID) && !defined(OS_CHROMEOS)
 MidiManager* MidiManager::Create() {
   return new MidiManager;
 }
 #endif
 
 MidiManager::MidiManager()
     : initialized_(false),
       result_(MIDI_NOT_SUPPORTED) {
 }
 
 MidiManager::~MidiManager() {
 }
 
 void MidiManager::StartSession(MidiManagerClient* client, int client_id) {
   bool session_is_ready;
   bool session_needs_initialization = false;
 
   {
-    base::AutoLock auto_lock(clients_lock_);
+    base::AutoLock auto_lock(lock_);
     session_is_ready = initialized_;
     if (!session_is_ready) {
       // Call StartInitialization() only for the first request.
       session_needs_initialization = pending_clients_.empty();
       pending_clients_.insert(
           std::pair<int, MidiManagerClient*>(client_id, client));
     }
   }
 
   // Lazily initialize the MIDI back-end.
   if (!session_is_ready) {
     if (session_needs_initialization) {
       TRACE_EVENT0("midi", "MidiManager::StartInitialization");
+      session_thread_runner_ =
+          base::MessageLoop::current()->message_loop_proxy();
       StartInitialization();
     }
     // CompleteInitialization() will be called asynchronously when platform
     // dependent initialization is finished.
     return;
   }
 
   // Platform dependent initialization was already finished for previously
   // initialized clients.
   MidiResult result;
   {
-    base::AutoLock auto_lock(clients_lock_);
+    base::AutoLock auto_lock(lock_);
     if (result_ == MIDI_OK)
       clients_.insert(client);
     result = result_;
   }
   client->CompleteStartSession(client_id, result);
 }
 
 void MidiManager::EndSession(MidiManagerClient* client) {
-  base::AutoLock auto_lock(clients_lock_);
+  base::AutoLock auto_lock(lock_);
   ClientList::iterator i = clients_.find(client);
   if (i != clients_.end())
     clients_.erase(i);
 }
 
 void MidiManager::DispatchSendMidiData(MidiManagerClient* client,
                                        uint32 port_index,
                                        const std::vector<uint8>& data,
                                        double timestamp) {
   NOTREACHED();
 }
 
 void MidiManager::StartInitialization() {
   CompleteInitialization(MIDI_NOT_SUPPORTED);
 }
 
 void MidiManager::CompleteInitialization(MidiResult result) {
-  TRACE_EVENT0("midi", "MidiManager::CompleteInitialization");
-
-  base::AutoLock auto_lock(clients_lock_);
-  DCHECK(clients_.empty());
-  DCHECK(!pending_clients_.empty());
-  DCHECK(!initialized_);
-  initialized_ = true;
-  result_ = result;
-
-  for (PendingClientMap::iterator it = pending_clients_.begin();
-       it != pending_clients_.end();
-       ++it) {
-    if (result_ == MIDI_OK)
-      clients_.insert(it->second);
-    it->second->CompleteStartSession(it->first, result_);
-  }
-  pending_clients_.clear();
+  DCHECK(session_thread_runner_.get());
+  // It is safe to post a task to the IO thread from here because the IO thread
+  // should have stopped if the MidiManager is going to be destructed.
+  session_thread_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&MidiManager::CompleteInitializationInternal,
+                 base::Unretained(this),
+                 result));
 }
 
 void MidiManager::AddInputPort(const MidiPortInfo& info) {
   input_ports_.push_back(info);
 }
 
 void MidiManager::AddOutputPort(const MidiPortInfo& info) {
   output_ports_.push_back(info);
 }
 
 void MidiManager::ReceiveMidiData(
     uint32 port_index,
     const uint8* data,
     size_t length,
     double timestamp) {
-  base::AutoLock auto_lock(clients_lock_);
+  base::AutoLock auto_lock(lock_);
 
   for (ClientList::iterator i = clients_.begin(); i != clients_.end(); ++i)
     (*i)->ReceiveMidiData(port_index, data, length, timestamp);
 }
 
+void MidiManager::CompleteInitializationInternal(MidiResult result) {
+  TRACE_EVENT0("midi", "MidiManager::CompleteInitialization");
+
+  base::AutoLock auto_lock(lock_);
+  DCHECK(clients_.empty());
+  DCHECK(!pending_clients_.empty());
+  DCHECK(!initialized_);
+  initialized_ = true;
+  result_ = result;
+
+  for (PendingClientMap::iterator it = pending_clients_.begin();
+       it != pending_clients_.end();
+       ++it) {
+    if (result_ == MIDI_OK)
+      clients_.insert(it->second);
+    it->second->CompleteStartSession(it->first, result_);
+  }
+  pending_clients_.clear();
+}
+
 }  // namespace media