Introduce PlatformThread::Detach

base/threading/platform_thread.h

 // 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.
 
 // WARNING: You should *NOT* be using this class directly.  PlatformThread is
 // the low-level platform-specific abstraction to the OS's threading interface.
 // You should instead be using a message-loop driven Thread, see thread.h.
 
 #ifndef BASE_THREADING_PLATFORM_THREAD_H_
 #define BASE_THREADING_PLATFORM_THREAD_H_
@@ skipping 162 matching lines @@
   // CreateNonJoinable() does the same thing as Create() except the thread
   // cannot be Join()'d.  Therefore, it also does not output a
   // PlatformThreadHandle.
   static bool CreateNonJoinable(size_t stack_size, Delegate* delegate);
 
   // Joins with a thread created via the Create function.  This function blocks
   // the caller until the designated thread exits.  This will invalidate
   // |thread_handle|.
   static void Join(PlatformThreadHandle thread_handle);
 
+  // Detaches and releases the thread handle. The thread is no longer joinable
+  // after this call.

[danakj, 2016/06/09 22:58:07]

And the PlatformThreadHandle becomes invalid?

On windows this has no effect if the thread is the current thread. What happens
on posix? Do we want to support this?

[robliao, 2016/06/10 14:24:31]

Yup, the PlatformThreadHandle becomes invalid. Updated comment.

I think what you mean is Windows is okay if the handle represents the current
thread. Yes, as handles apply to the entire process. POSIX doesn't seem to mind
either (return value 0). Since the underlying platforms support it, I think it's
fine if we support it as well. I don't see a reason why not.

+  static void Detach(PlatformThreadHandle thread_handle);
+
   // Toggles the current thread's priority at runtime. A thread may not be able
   // to raise its priority back up after lowering it if the process does not
   // have a proper permission, e.g. CAP_SYS_NICE on Linux. A thread may not be
   // able to lower its priority back down after raising it to REALTIME_AUDIO.
   // Since changing other threads' priority is not permitted in favor of
   // security, this interface is restricted to change only the current thread
   // priority (https://crbug.com/399473).
   static void SetCurrentThreadPriority(ThreadPriority priority);
 
   static ThreadPriority GetCurrentThreadPriority();
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_PLATFORM_THREAD_H_