Add payload checksum to code cache data.

src/serialize.h

 // 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.
 
 #ifndef V8_SERIALIZE_H_
 #define V8_SERIALIZE_H_
 
 #include "src/compiler.h"
 #include "src/hashmap.h"
 #include "src/heap-profiler.h"
@@ skipping 928 matching lines @@
   Vector<const Reservation> Reservations() const;
   Vector<const byte> Payload() const;
 
   int NumInternalizedStrings() const;
   Vector<const uint32_t> CodeStubKeys() const;
 
  private:
   explicit SerializedCodeData(ScriptData* data)
       : SerializedData(const_cast<byte*>(data->data()), data->length()) {}
 
-  bool IsSane(String* source);
+  bool IsSane(String* source) const;
 
-  uint32_t SourceHash(String* source) { return source->length(); }
+  uint32_t SourceHash(String* source) const { return source->length(); }
 
   // The data header consists of int-sized entries:
   // [0] version hash
   // [1] source hash
   // [2] cpu features
   // [3] flag hash
   // [4] number of internalized strings
   // [5] number of code stub keys
   // [6] number of reservation size entries
   // [7] payload length
   static const int kVersionHashOffset = 0;
   static const int kSourceHashOffset = 1;
   static const int kCpuFeaturesOffset = 2;
   static const int kFlagHashOffset = 3;
   static const int kNumInternalizedStringsOffset = 4;
   static const int kReservationsOffset = 5;
   static const int kNumCodeStubKeysOffset = 6;
   static const int kPayloadLengthOffset = 7;
-  static const int kHeaderSize = (kPayloadLengthOffset + 1) * kIntSize;
+  static const int kChecksum1Offset = 8;
+  static const int kChecksum2Offset = 9;
+  static const int kHeaderSize =
+      POINTER_SIZE_ALIGN((kChecksum2Offset + 1) * kIntSize);
 };
 } }  // namespace v8::internal
 
 #endif  // V8_SERIALIZE_H_