Move autowrap from ThreadManager constructor to Thread::Current.

webrtc/base/thread.cc

Index: webrtc/base/thread.cc
diff --git a/webrtc/base/thread.cc b/webrtc/base/thread.cc
index 66542bb3d90712cfc927d1d9f225e2055aacaddf..f48f0f78be24dd8af4aac0b3be70d3754525cc81 100644
--- a/webrtc/base/thread.cc
+++ b/webrtc/base/thread.cc
@@ -31,23 +31,24 @@ ThreadManager* ThreadManager::Instance() {
   return &thread_manager;
 }
 
+ThreadManager::~ThreadManager() {
+  // By above RTC_DEFINE_STATIC_LOCAL.
+  RTC_NOTREACHED() << "ThreadManager should never be destructed.";

[Taylor Brandstetter, 2017/04/21 09:54:28]

But it has a public constructor/destructor, so a native application could
construct it explicitly as opposed to using "Instance()". If we expect everyone
to go through "Instance", we should go a step further and make the constructor
private. Otherwise, we should remove the RTC_NOTREACHED(), and unwrap threads on
destruction.

[nisse-webrtc, 2017/04/21 11:06:07]

I'd prefer to not add the bookkeeping needed to unwrap threads. I could try
making constructor and destructor private. Do we have any other conventions on
how to do singletons (fancy name for global variable) like this?

BTW, according to
http://stackoverflow.com/questions/246564/what-is-the-lifetime-of-a-static-va...,
initialization of static locals like this are thread safe at least from C++11.
Which was news to me.

[Taylor Brandstetter, 2017/04/21 11:32:54]

Let's try making the constructor/destructor private and see if anyone notices. I
couldn't find any code that uses them.

I'm unaware of any singleton conventions we have, though just keeping
"Instance()" for now seems fine.

And yeah, static locals are pretty convenient. I don't think I've encountered
any problems yet with this approach to a singleton.

+}
+
 // static
 Thread* Thread::Current() {
+#ifdef NO_MAIN_THREAD_WRAPPING
   return ThreadManager::Instance()->CurrentThread();
+#else
+  return ThreadManager::Instance()->WrapCurrentThread();
+#endif
 }
 
 #if defined(WEBRTC_POSIX)
 #if !defined(WEBRTC_MAC)
 ThreadManager::ThreadManager() {
   pthread_key_create(&key_, nullptr);
-#ifndef NO_MAIN_THREAD_WRAPPING
-  WrapCurrentThread();
-#endif
-}
-
-ThreadManager::~ThreadManager() {
-  UnwrapCurrentThread();
-  pthread_key_delete(key_);
 }
 #endif
 
@@ -63,14 +64,6 @@ void ThreadManager::SetCurrentThread(Thread *thread) {
 #if defined(WEBRTC_WIN)
 ThreadManager::ThreadManager() {
   key_ = TlsAlloc();
-#ifndef NO_MAIN_THREAD_WRAPPING
-  WrapCurrentThread();
-#endif
-}
-
-ThreadManager::~ThreadManager() {
-  UnwrapCurrentThread();
-  TlsFree(key_);
 }
 
 Thread *ThreadManager::CurrentThread() {