Enable the FileDescriptorWatcher API on MessageLoopForIO threads.

base/threading/thread.cc

 // Copyright (c) 2012 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 "base/threading/thread.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/lazy_instance.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/run_loop.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 #include "base/threading/thread_id_name_manager.h"
 #include "base/threading/thread_local.h"
 #include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
 
+#if defined(OS_POSIX) && !defined(OS_NACL_SFI)
+#include "base/files/file_descriptor_watcher_posix.h"
+#endif
+
 #if defined(OS_WIN)
 #include "base/win/scoped_com_initializer.h"
 #endif
 
 namespace base {
 
 namespace {
 
 // We use this thread-local variable to record whether or not a thread exited
 // because its Stop method was called.  This allows us to catch cases where
@@ skipping 258 matching lines @@
   // Complete the initialization of our Thread object.
   PlatformThread::SetName(name_.c_str());
   ANNOTATE_THREAD_NAME(name_.c_str());  // Tell the name to race detector.
 
   // Lazily initialize the |message_loop| so that it can run on this thread.
   DCHECK(message_loop_);
   std::unique_ptr<MessageLoop> message_loop(message_loop_);
   message_loop_->BindToCurrentThread();
   message_loop_->SetTimerSlack(message_loop_timer_slack_);
 
+#if defined(OS_POSIX) && !defined(OS_NACL_SFI)
+  // Allow threads running a MessageLoopForIO to use FileDescriptorWatcher API.
+  std::unique_ptr<FileDescriptorWatcher> file_descriptor_watcher;
+  if (MessageLoopForIO::IsCurrent()) {
+    file_descriptor_watcher.reset(
+        new FileDescriptorWatcher(MessageLoopForIO::current()));

[dcheng, 2016/09/26 17:34:40]

Is there a time when this wouldn't return the same value as |message_loop_|?

[fdoray, 2016/09/26 17:44:07]

No.

message_loop_->BindToCurrentThread() above sets the TLS returned by
MessageLoopForIO::current(). Added DCHECK.

+  }
+#endif
+
 #if defined(OS_WIN)
   std::unique_ptr<win::ScopedCOMInitializer> com_initializer;
   if (com_status_ != NONE) {
     com_initializer.reset((com_status_ == STA) ?
         new win::ScopedCOMInitializer() :
         new win::ScopedCOMInitializer(win::ScopedCOMInitializer::kMTA));
   }
 #endif
 
   // Let the thread do extra initialization.
@@ skipping 35 matching lines @@
   run_loop_ = nullptr;
 }
 
 void Thread::ThreadQuitHelper() {
   DCHECK(run_loop_);
   run_loop_->QuitWhenIdle();
   SetThreadWasQuitProperly(true);
 }
 
 }  // namespace base