VM: Fix crash in profile signal handler.

runtime/vm/thread_registry.cc

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/thread_registry.h"
 
 #include "vm/isolate.h"
 #include "vm/lockers.h"
 
 namespace dart {
@@ skipping 88 matching lines @@
 }
 
 
 void ThreadRegistry::Unschedule(Thread* thread,
                                 bool is_mutator,
                                 bool bypass_safepoint) {
   MonitorLocker ml(monitor_);
   OSThread* os_thread = thread->os_thread();
   ASSERT(os_thread != NULL);
   os_thread->DisableThreadInterrupts();
+  os_thread->set_thread(NULL);
+  OSThread::SetCurrent(os_thread);
   thread->isolate_ = NULL;
   thread->heap_ = NULL;
   thread->set_os_thread(NULL);
-  os_thread->set_thread(NULL);
-  OSThread::SetCurrent(os_thread);
   if (!is_mutator) {
     ASSERT(thread->api_top_scope() == NULL);
     ReturnThreadToFreelist(thread);
   }
   if (!bypass_safepoint && in_rendezvous_) {
     // Don't wait for this thread.
     ASSERT(remaining_ > 0);
     if (--remaining_ == 0) {
       ml.NotifyAll();
     }
@@ skipping 96 matching lines @@
   intptr_t count = 0;
   Thread* current = active_list_;
   while (current != NULL) {
     ++count;
     current = current->next_;
   }
   return count;
 }
 
 }  // namespace dart