Serializer: canonicalize cleared weak cells.

src/snapshot/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_SNAPSHOT_SERIALIZE_H_
 #define V8_SNAPSHOT_SERIALIZE_H_
 
 #include "src/hashmap.h"
 #include "src/heap-profiler.h"
 #include "src/isolate.h"
@@ skipping 355 matching lines @@
   // ---------- Misc ----------
   // Skip.
   static const int kSkip = 0x1d;
   // Internal reference encoded as offsets of pc and target from code entry.
   static const int kInternalReference = 0x1e;
   static const int kInternalReferenceEncoded = 0x1f;
   // Do nothing, used for padding.
   static const int kNop = 0x3d;
   // Move to next reserved chunk.
   static const int kNextChunk = 0x3e;
+  // Canonical cleared weak cell.
+  static const int kClearedWeakCell = 0x3f;
   // A tag emitted at strategic points in the snapshot to delineate sections.
   // If the deserializer does not find these at the expected moments then it
   // is an indication that the snapshot and the VM do not fit together.
   // Examine the build process for architecture, version or configuration
   // mismatches.
   static const int kSynchronize = 0x5d;
   // Used for the source code of the natives, which is in the executable, but
   // is referred to from external strings in the snapshot.
   static const int kNativesStringResource = 0x5e;
   // Raw data of variable length.
@@ skipping 609 matching lines @@
       kNumInternalizedStringsOffset + kInt32Size;
   static const int kNumCodeStubKeysOffset = kNumReservationsOffset + kInt32Size;
   static const int kPayloadLengthOffset = kNumCodeStubKeysOffset + kInt32Size;
   static const int kChecksum1Offset = kPayloadLengthOffset + kInt32Size;
   static const int kChecksum2Offset = kChecksum1Offset + kInt32Size;
   static const int kHeaderSize = kChecksum2Offset + kInt32Size;
 };
 } }  // namespace v8::internal
 
 #endif  // V8_SNAPSHOT_SERIALIZE_H_