Avoid unnecessary byte-swapping in blink's SerializedScriptValue.

third_party/WebKit/Source/bindings/core/v8/SerializedScriptValue.h

 /*
  * Copyright (C) 2009, 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 57 matching lines @@
   // Version 3: Switched to using uuids as blob data identifiers.
   // Version 4: Extended File serialization to be complete.
   // Version 5: Added CryptoKeyTag for Key objects.
   // Version 6: Added indexed serialization for File, Blob, and FileList.
   // Version 7: Extended File serialization with user visibility.
   // Version 8: File.lastModified in milliseconds (seconds-based in earlier
   //            versions.)
   // Version 9: Added Map and Set support.
   // [versions skipped]
   // Version 16: Separate versioning between V8 and Blink.
-  static const uint32_t wireFormatVersion = 16;
+  // Version 17: Remove unnecessary byte flipping in wire format.
+  //
+  // The following versions cannot be used, in order to be able to
+  // deserialize version 0 SSVs. The class implementation has details.
+  // DO NOT USE: 35, 64, 68, 73, 78, 82, 83, 85, 91, 98, 102, 108, 123.

[jsbell, 2017/04/07 23:40:34]

static_assert() please!

[pwnall, 2017/04/08 01:09:08]

Done.
Thanks for the suggestion! That's a great idea! I placed the static_assert near
the code that uses the assumption, to help a curious developer who might tinker
with this code.

+  static const uint32_t wireFormatVersion = 17;
 
   struct SerializeOptions {
     STACK_ALLOCATED();
     Transferables* transferables = nullptr;
     WebBlobInfoArray* blobInfo = nullptr;
     bool writeWasmToStream = false;
   };
   static PassRefPtr<SerializedScriptValue> serialize(v8::Isolate*,
                                                      v8::Local<v8::Value>,
                                                      const SerializeOptions&,
@@ skipping 129 matching lines @@
       ExceptionState& exceptionState) {
     return SerializedScriptValue::serialize(
         isolate, value, SerializedScriptValue::SerializeOptions(),
         exceptionState);
   }
 };
 
 }  // namespace blink
 
 #endif  // SerializedScriptValue_h