Fix sticky error propagation from thread to isolate

runtime/vm/isolate.cc

 // Copyright (c) 2013, 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/isolate.h"
 
 #include "include/dart_api.h"
 #include "include/dart_native_api.h"
 #include "platform/assert.h"
 #include "platform/text_buffer.h"
@@ skipping 2574 matching lines @@
                                bool is_mutator,
                                bool bypass_safepoint) {
   // Disassociate the 'Thread' structure and unschedule the thread
   // from this isolate.
   // We are disassociating the thread from an isolate and it would
   // not be possible to correctly track no_safepoint_scope_depth for the
   // thread in the constructor/destructor of MonitorLocker,
   // so we create a MonitorLocker object which does not do any
   // no_safepoint_scope_depth increments/decrements.
   MonitorLocker ml(threads_lock(), false);
+  thread->isolate()->object_store()->SetStickyErrorFromThread(thread);

[siva, 2016/03/08 08:54:59]

If multiple threads exit at the same time won't this  result in the sticky error
being overwritten to the one exiting last.

[srdjan, 2016/03/08 20:21:09]

Modified code to allow only mutator thread to propagate sticky error to isolate.
'SetStickyError' checks that a sticky error is not overwritten.

   if (!bypass_safepoint) {
     // Ensure that the thread reports itself as being at a safepoint.
     thread->EnterSafepoint();
   }
   OSThread* os_thread = thread->os_thread();
   ASSERT(os_thread != NULL);
   os_thread->DisableThreadInterrupts();
   os_thread->set_thread(NULL);
   OSThread::SetCurrent(os_thread);
   if (is_mutator) {
     mutator_thread_ = NULL;
   }
   thread->isolate_ = NULL;
   thread->heap_ = NULL;
   thread->set_os_thread(NULL);
   thread->set_execution_state(Thread::kThreadInVM);
   thread->set_safepoint_state(0);
   thread->clear_pending_functions();
+  thread->clear_sticky_error();
   ASSERT(thread->no_safepoint_scope_depth() == 0);
   // Return thread structure.
   thread_registry()->ReturnThreadLocked(is_mutator, thread);
 }
 
 
 static RawInstance* DeserializeObject(Thread* thread,
                                       uint8_t* obj_data,
                                       intptr_t obj_len) {
   if (obj_data == NULL) {
@@ skipping 216 matching lines @@
 void IsolateSpawnState::DecrementSpawnCount() {
   ASSERT(spawn_count_monitor_ != NULL);
   ASSERT(spawn_count_ != NULL);
   MonitorLocker ml(spawn_count_monitor_);
   ASSERT(*spawn_count_ > 0);
   *spawn_count_ = *spawn_count_ - 1;
   ml.Notify();
 }
 
 }  // namespace dart