Web MIDI: add dynamic MidiManager instantiation support for Linux

media/midi/midi_manager.cc

Index: media/midi/midi_manager.cc
diff --git a/media/midi/midi_manager.cc b/media/midi/midi_manager.cc
index 95a48401c09781a26f3fceff88153bff45c03b0e..420163547162d9ea0ea53de3bdf59e098e762772 100644
--- a/media/midi/midi_manager.cc
+++ b/media/midi/midi_manager.cc
@@ -46,10 +46,11 @@ void ReportUsage(Usage usage) {
 
 }  // namespace
 
-MidiManager::MidiManager()
+MidiManager::MidiManager(MidiService* service)
     : initialization_state_(InitializationState::NOT_STARTED),
       finalized_(false),
-      result_(Result::NOT_INITIALIZED) {
+      result_(Result::NOT_INITIALIZED),
+      service_(service) {
   ReportUsage(Usage::CREATED);
 }
 
@@ -62,9 +63,9 @@ MidiManager::~MidiManager() {
 
 #if !defined(OS_MACOSX) && !defined(OS_WIN) && \
     !(defined(USE_ALSA) && defined(USE_UDEV)) && !defined(OS_ANDROID)
-MidiManager* MidiManager::Create() {
+MidiManager* MidiManager::Create(MidiService* service) {
   ReportUsage(Usage::CREATED_ON_UNSUPPORTED_PLATFORMS);
-  return new MidiManager;
+  return new MidiManager(service);
 }
 #endif
 
@@ -72,15 +73,24 @@ void MidiManager::Shutdown() {
   UMA_HISTOGRAM_ENUMERATION("Media.Midi.ResultOnShutdown",
                             static_cast<int>(result_),
                             static_cast<int>(Result::MAX) + 1);
-  base::AutoLock auto_lock(lock_);
-  if (session_thread_runner_) {
-    session_thread_runner_->PostTask(
-        FROM_HERE, base::Bind(&MidiManager::ShutdownOnSessionThread,
-                              base::Unretained(this)));
-    session_thread_runner_ = nullptr;
-  } else {
-    finalized_ = true;
+  bool shutdown_synchronously = false;
+  {
+    base::AutoLock auto_lock(lock_);
+    if (session_thread_runner_) {
+      if (session_thread_runner_->BelongsToCurrentThread()) {
+        shutdown_synchronously = true;
+      } else {
+        session_thread_runner_->PostTask(
+            FROM_HERE, base::Bind(&MidiManager::ShutdownOnSessionThread,
+                                  base::Unretained(this)));
+      }
+      session_thread_runner_ = nullptr;
+    } else {
+      finalized_ = true;
+    }
   }
+  if (shutdown_synchronously)
+    ShutdownOnSessionThread();
 }
 
 void MidiManager::StartSession(MidiManagerClient* client) {