Don't take a stack trace if we are in the middle of a deoptimization

runtime/vm/isolate.h

 // 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.
 
 #ifndef VM_ISOLATE_H_
 #define VM_ISOLATE_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/atomic.h"
@@ skipping 354 matching lines @@
     return shutdown_callback_;
   }
 
   void set_object_id_ring(ObjectIdRing* ring) {
     object_id_ring_ = ring;
   }
   ObjectIdRing* object_id_ring() {
     return object_id_ring_;
   }
 
+  bool IsDeoptimizing() const { return deopt_context_ != NULL; }
   DeoptContext* deopt_context() const { return deopt_context_; }
   void set_deopt_context(DeoptContext* value) {
     ASSERT(value == NULL || deopt_context_ == NULL);
     deopt_context_ = value;
   }
 
   BackgroundCompiler* background_compiler() const {
     return background_compiler_;
   }
   void set_background_compiler(BackgroundCompiler* value) {
@@ skipping 517 matching lines @@
   intptr_t* spawn_count_;
 
   Dart_IsolateFlags isolate_flags_;
   bool paused_;
   bool errors_are_fatal_;
 };
 
 }  // namespace dart
 
 #endif  // VM_ISOLATE_H_