Revert of Reland #1: "base: Implement GetCurrentThreadPriority."

base/threading/platform_thread_mac.mm

 // 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/platform_thread.h"
 
 #import <Foundation/Foundation.h>
 #include <mach/mach.h>
 #include <mach/mach_time.h>
 #include <mach/thread_policy.h>
@@ skipping 187 matching lines @@
     return ThreadPriority::NORMAL;
 
   ThreadPriority thread_priority =
       static_cast<ThreadPriority>(priority.intValue);
   switch (thread_priority) {
     case ThreadPriority::BACKGROUND:
     case ThreadPriority::NORMAL:
     case ThreadPriority::DISPLAY:
     case ThreadPriority::REALTIME_AUDIO:
       return thread_priority;
+    default:
+      NOTREACHED() << "Unknown priority.";
+      return ThreadPriority::NORMAL;
   }
-  NOTREACHED() << "Unknown priority.";
-  return ThreadPriority::NORMAL;
 }
 
 size_t GetDefaultThreadStackSize(const pthread_attr_t& attributes) {
 #if defined(OS_IOS)
   return 0;
 #else
   // The Mac OS X default for a pthread stack size is 512kB.
   // Libc-594.1.4/pthreads/pthread.c's pthread_attr_init uses
   // DEFAULT_STACK_SIZE for this purpose.
   //
@@ skipping 21 matching lines @@
                  static_cast<size_t>(stack_rlimit.rlim_cur));
   }
   return default_stack_size;
 #endif
 }
 
 void TerminateOnThread() {
 }
 
 }  // namespace base