[serializer] API to re-use global proxy in v8::Context::FromSnapshot.

src/snapshot/snapshot-common.cc

 // Copyright 2006-2008 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.
 
 // The common functionality when building with or without snapshots.
 
 #include "src/snapshot/snapshot.h"
 
 #include "src/api.h"
 #include "src/base/platform/platform.h"
@@ skipping 44 matching lines @@
   if (!isolate->snapshot_available()) return Handle<Context>();
   base::ElapsedTimer timer;
   if (FLAG_profile_deserialization) timer.Start();
 
   const v8::StartupData* blob = isolate->snapshot_blob();
   Vector<const byte> context_data =
       ExtractContextData(blob, static_cast<int>(context_index));
   SnapshotData snapshot_data(context_data);
   Deserializer deserializer(&snapshot_data);
 
-  if (context_index > 0) {
-    // A non-default context uses the global proxy from the snapshot.
-    DCHECK(global_proxy.is_null());
-  }
-
   MaybeHandle<Object> maybe_context =
       deserializer.DeserializePartial(isolate, global_proxy);
   Handle<Object> result;
   if (!maybe_context.ToHandle(&result)) return MaybeHandle<Context>();
   CHECK(result->IsContext());
   if (FLAG_profile_deserialization) {
     double ms = timer.Elapsed().InMillisecondsF();
     int bytes = context_data.length();
     PrintF("[Deserializing context #%zu (%d bytes) took %0.3f ms]\n",
            context_index, bytes, ms);
@@ skipping 145 matching lines @@
 Vector<const byte> SnapshotData::Payload() const {
   int reservations_size = GetHeaderValue(kNumReservationsOffset) * kInt32Size;
   const byte* payload = data_ + kHeaderSize + reservations_size;
   int length = GetHeaderValue(kPayloadLengthOffset);
   DCHECK_EQ(data_ + size_, payload + length);
   return Vector<const byte>(payload, length);
 }
 
 }  // namespace internal
 }  // namespace v8