[wasm] Support recompilation if deserialization fails.

src/snapshot/code-serializer.h

 // Copyright 2016 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_CODE_SERIALIZER_H_
 #define V8_SNAPSHOT_CODE_SERIALIZER_H_
 
 #include "src/parsing/preparse-data.h"
 #include "src/snapshot/serializer.h"
 
@@ skipping 74 matching lines @@
 // Wrapper around ScriptData to provide code-serializer-specific functionality.
 class SerializedCodeData : public SerializedData {
  public:
   enum SanityCheckResult {
     CHECK_SUCCESS = 0,
     MAGIC_NUMBER_MISMATCH = 1,
     VERSION_MISMATCH = 2,
     SOURCE_MISMATCH = 3,
     CPU_FEATURES_MISMATCH = 4,
     FLAGS_MISMATCH = 5,
-    CHECKSUM_MISMATCH = 6
+    CHECKSUM_MISMATCH = 6,
+    INVALID_HEADER = 7

[Yang, 2016/10/06 07:35:34]

Don't forget to add this item to
chromium/src/tools/metrics/histograms/histograms.xml, look for
"V8CodeCacheRejectReason"

[Mircea Trofin, 2016/10/06 16:17:47]

Acknowledged. Didn't know about that entire area, thanks!

   };
 
   // Used when consuming.
   static const SerializedCodeData FromCachedData(
       Isolate* isolate, ScriptData* cached_data, uint32_t expected_source_hash,
       SanityCheckResult* rejection_result);
 
   // Used when producing.
   SerializedCodeData(const List<byte>* payload, const CodeSerializer* cs);
 
@@ skipping 41 matching lines @@
   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 internal
 }  // namespace v8
 
 #endif  // V8_SNAPSHOT_CODE_SERIALIZER_H_