Do not rely on uniquiness of pthread_t

src/top.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 51 matching lines @@
 #endif
 #ifdef ENABLE_LOGGING_AND_PROFILING
   js_entry_sp_ = NULL;
   external_callback_ = NULL;
 #endif
 #ifdef ENABLE_VMSTATE_TRACKING
   current_vm_state_ = EXTERNAL;
 #endif
   try_catch_handler_address_ = NULL;
   context_ = NULL;
-  int id = Isolate::Current()->thread_manager()->CurrentId();
-  thread_id_ = (id == 0) ? ThreadManager::kInvalidId : id;
+  thread_id_ = ThreadId::Current();
   external_caught_exception_ = false;
   in_exception_reporting_ = false;
   failed_access_check_callback_ = NULL;
   save_context_ = NULL;
   catcher_ = NULL;
 }
 
 
 Address Isolate::get_address_from_id(Isolate::AddressId id) {
   return isolate_addresses_[id];
@@ skipping 877 matching lines @@
   thread_local_top()->simulator_ = Simulator::current(this);
 #endif
 #endif
   if (RuntimeProfiler::IsEnabled() && current_vm_state() == JS) {
     RuntimeProfiler::IsolateEnteredJS(this);
   }
   return from + sizeof(ThreadLocalTop);
 }
 
 } }  // namespace v8::internal