SnapshotCreator: start from existing snapshot if we have one

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 177 matching lines @@
 
   // Calculate sizes.
   int reservation_size = reservations.length() * kInt32Size;
   int size = kHeaderSize + reservation_size + payload->length();
 
   // Allocate backing store and create result data.
   AllocateData(size);
 
   // Set header values.
   SetMagicNumber(serializer->isolate());
-  SetHeaderValue(kCheckSumOffset, Version::Hash());
+  SetHeaderValue(kVersionHashOffset, Version::Hash());
   SetHeaderValue(kNumReservationsOffset, reservations.length());
   SetHeaderValue(kPayloadLengthOffset, payload->length());
 
   // Copy reservation chunk sizes.
   CopyBytes(data_ + kHeaderSize, reinterpret_cast<byte*>(reservations.begin()),
             reservation_size);
 
   // Copy serialized data.
   CopyBytes(data_ + kHeaderSize + reservation_size, payload->begin(),
             static_cast<size_t>(payload->length()));
 }
 
 bool SnapshotData::IsSane() {
-  return GetHeaderValue(kCheckSumOffset) == Version::Hash();
+  return GetHeaderValue(kVersionHashOffset) == Version::Hash();
 }
 
 Vector<const SerializedData::Reservation> SnapshotData::Reservations() const {
   return Vector<const Reservation>(
       reinterpret_cast<const Reservation*>(data_ + kHeaderSize),
       GetHeaderValue(kNumReservationsOffset));
 }
 
 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