Add a flag to track detached contexts.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 21ac999f8a5cc6f682b9633166f2f9fde1c04a2e..4fb8272cf5b7da77d2b1275cb03615d947e7b296 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -1141,6 +1141,9 @@ class Isolate {
     return store_buffer_hash_set_2_address_;
   }
 
+  void AddDetachedContext(Handle<Context> context);
+  void CheckDetachedContextsAfterGC();
+
  private:
   explicit Isolate(bool enable_serializer);
 
@@ -1362,6 +1365,7 @@ class Isolate {
   v8::Isolate::UseCounterCallback use_counter_callback_;
   BasicBlockProfiler* basic_block_profiler_;
 
+
   friend class ExecutionAccess;
   friend class HandleScopeImplementer;
   friend class OptimizingCompilerThread;