Add a flag to track detached contexts.

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 836 matching lines @@
 
     {
       HistogramTimerScope histogram_timer_scope(
           (collector == SCAVENGER) ? isolate_->counters()->gc_scavenger()
                                    : isolate_->counters()->gc_compactor());
       next_gc_likely_to_collect_more =
           PerformGarbageCollection(collector, gc_callback_flags);
     }
 
     GarbageCollectionEpilogue();
+    if (collector == MARK_COMPACTOR && FLAG_track_detached_contexts) {
+      isolate()->CheckDetachedContextsAfterGC();
+    }
     tracer()->Stop(collector);
   }
 
   // Start incremental marking for the next cycle. The heap snapshot
   // generator needs incremental marking to stay off after it aborted.
   if (!mark_compact_collector()->abort_incremental_marking() &&
       WorthActivatingIncrementalMarking()) {
     incremental_marking()->Start();
   }
 
@@ skipping 2197 matching lines @@
     Handle<TypeFeedbackVector> dummy_vector =
         factory->NewTypeFeedbackVector(spec);
     dummy_vector->Set(FeedbackVectorICSlot(0),
                       *TypeFeedbackVector::MegamorphicSentinel(isolate()),
                       SKIP_WRITE_BARRIER);
     set_keyed_load_dummy_vector(*dummy_vector);
   } else {
     set_keyed_load_dummy_vector(empty_fixed_array());
   }
 
+  set_detached_contexts(empty_fixed_array());
+
   Handle<SeededNumberDictionary> slow_element_dictionary =
       SeededNumberDictionary::New(isolate(), 0, TENURED);
   slow_element_dictionary->set_requires_slow_elements();
   set_empty_slow_element_dictionary(*slow_element_dictionary);
 
   set_materialized_objects(*factory->NewFixedArray(0, TENURED));
 
   // Handling of script id generation is in Factory::NewScript.
   set_last_script_id(Smi::FromInt(v8::UnboundScript::kNoScriptId));
 
@@ skipping 3403 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 }
 }  // namespace v8::internal