Fix for issue 27019 (Safepoint assertion failure in Flutter)

BUG=27019
R=rmacnak@google.com

Review URL: https://codereview.chromium.org/2215523002 .

runtime/vm/isolate.cc

@@ -2595,7 +2595,8 @@ Thread* Isolate::ScheduleThread(bool is_mutator, bool bypass_safepoint) {
     ASSERT(heap() != NULL);
     thread->heap_ = heap();
     thread->set_os_thread(os_thread);
-    ASSERT(thread->execution_state() == Thread::kThreadInVM);
+    ASSERT(thread->execution_state() == Thread::kThreadInNative);
+    thread->set_execution_state(Thread::kThreadInVM);
     thread->set_safepoint_state(0);
     thread->set_vm_tag(VMTag::kVMTagId);
     ASSERT(thread->no_safepoint_scope_depth() == 0);
@@ -2646,8 +2647,8 @@ void Isolate::UnscheduleThread(Thread* thread,
   thread->isolate_ = NULL;
   thread->heap_ = NULL;
   thread->set_os_thread(NULL);
-  thread->set_execution_state(Thread::kThreadInVM);
-  thread->set_safepoint_state(0);
+  thread->set_execution_state(Thread::kThreadInNative);
+  thread->set_safepoint_state(Thread::SetAtSafepoint(true, 0));
   thread->clear_pending_functions();
   ASSERT(thread->no_safepoint_scope_depth() == 0);
   // Return thread structure.

runtime/vm/profiler.cc

@@ -949,7 +949,9 @@ static uintptr_t __attribute__((noinline)) GetProgramCounter() {
 
 void Profiler::DumpStackTrace(bool native_stack_trace) {
   Thread* thread = Thread::Current();
-  ASSERT(thread != NULL);
+  if (thread == NULL) {
+    return;
+  }
   OSThread* os_thread = thread->os_thread();
   ASSERT(os_thread != NULL);
   Isolate* isolate = thread->isolate();

runtime/vm/thread.cc

@@ -97,7 +97,7 @@ Thread::Thread(Isolate* isolate)
       REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_INITIALIZERS)
       REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_SCOPE_INIT)
       safepoint_state_(0),
-      execution_state_(kThreadInVM),
+      execution_state_(kThreadInNative),
       next_(NULL) {
 NOT_IN_PRODUCT(
   dart_stream_ = Timeline::GetDartStream();