[serializer] complete slack tracking when creating context snapshot.

src/api.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/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 607 matching lines @@
         *v8::Utils::OpenHandle(*data->default_context_.Get(data->isolate_));
     data->default_context_.Reset();
     for (int i = 0; i < num_additional_contexts; i++) {
       i::Handle<i::Context> context =
           v8::Utils::OpenHandle(*data->contexts_.Get(i));
       contexts.Add(*context);
     }
     data->contexts_.Clear();
   }
 
+  // Complete in-object slack tracking for all functions.
+  i::HeapIterator heap_iterator(isolate->heap());
+  while (i::HeapObject* current_obj = heap_iterator.next()) {
+    if (!current_obj->IsJSFunction()) continue;
+    i::JSFunction* fun = i::JSFunction::cast(current_obj);
+    fun->CompleteInobjectSlackTrackingIfActive();
+  }
+
 #ifdef DEBUG
   i::ExternalReferenceTable::instance(isolate)->ResetCount();
 #endif  // DEBUG
 
   i::StartupSerializer startup_serializer(isolate, function_code_handling);
   startup_serializer.SerializeStrongReferences();
 
   // Serialize each context with a new partial serializer.
   i::List<i::SnapshotData*> context_snapshots(num_additional_contexts + 1);
 
@@ skipping 9607 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8