Avoid unnecessary byte-swapping in blink's SerializedScriptValue.

third_party/WebKit/Source/bindings/modules/v8/V8BindingForModulesTest.cpp

 /*
  * Copyright (C) 2011 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 114 matching lines @@
                              int expected) {
   IDBKey* idb_key =
       CheckKeyFromValueAndKeyPathInternal(isolate, value, key_path);
   ASSERT_TRUE(idb_key);
   ASSERT_EQ(IDBKey::kNumberType, idb_key->GetType());
   ASSERT_TRUE(expected == idb_key->Number());
 }
 
 // SerializedScriptValue header format offsets are inferred from the Blink and
 // V8 serialization code. The code below DCHECKs that
-constexpr static size_t kSSVHeaderBlinkVersionOffset = 0;
-constexpr static size_t kSSVHeaderBlinkVersionTagOffset = 1;
-constexpr static size_t kSSVHeaderV8VersionOffset = 2;
-constexpr static size_t kSSVHeaderV8VersionTagOffset = 3;
-
-// 13 is v8::internal::kLatestVersion in v8/src/value-serializer.cc at the
-// time when this test was written. Unlike Blink, V8 does not currently export
-// its serialization version, so this number might get stale.
-constexpr static unsigned char kV8LatestKnownVersion = 13;
+constexpr static size_t kSSVHeaderBlinkVersionTagOffset = 0;
+constexpr static size_t kSSVHeaderBlinkVersionOffset = 1;
+constexpr static size_t kSSVHeaderV8VersionTagOffset = 2;
+constexpr static size_t kSSVHeaderV8VersionOffset = 3;
 
 // Follows the same steps as the IndexedDB value serialization code.
 void SerializeV8Value(v8::Local<v8::Value> value,
                       v8::Isolate* isolate,
                       Vector<char>* wire_bytes) {
   NonThrowableExceptionState non_throwable_exception_state;
 
   SerializedScriptValue::SerializeOptions options;
   RefPtr<SerializedScriptValue> serialized_value =
       SerializedScriptValue::Serialize(isolate, value, options,
                                        non_throwable_exception_state);
   serialized_value->ToWireBytes(*wire_bytes);
 
   // Sanity check that the serialization header has not changed, as the tests
   // that use this method rely on the header format.
   //
   // The cast from char* to unsigned char* is necessary to avoid VS2015 warning
   // C4309 (truncation of constant value). This happens because VersionTag is
   // 0xFF.
   const unsigned char* wire_data =
       reinterpret_cast<unsigned char*>(wire_bytes->Data());
+  ASSERT_EQ(static_cast<unsigned char>(kVersionTag),
+            wire_data[kSSVHeaderBlinkVersionTagOffset]);
   ASSERT_EQ(
       static_cast<unsigned char>(SerializedScriptValue::kWireFormatVersion),
       wire_data[kSSVHeaderBlinkVersionOffset]);
-  ASSERT_EQ(static_cast<unsigned char>(kVersionTag),
-            wire_data[kSSVHeaderBlinkVersionTagOffset]);
 
-  ASSERT_GE(static_cast<unsigned char>(kV8LatestKnownVersion),
-            wire_data[kSSVHeaderV8VersionOffset]);
   ASSERT_EQ(static_cast<unsigned char>(kVersionTag),
             wire_data[kSSVHeaderV8VersionTagOffset]);
+  ASSERT_EQ(v8::ValueSerializer::GetCurrentDataFormatVersion(),
+            wire_data[kSSVHeaderV8VersionOffset]);
 }
 
 PassRefPtr<IDBValue> CreateIDBValue(v8::Isolate* isolate,
                                     Vector<char>& wire_bytes,
                                     double primary_key,
                                     const WebString& key_path) {
   WebData web_data(SharedBuffer::AdoptVector(wire_bytes));
   Vector<WebBlobInfo> web_blob_info;
   WebIDBKey web_idb_key = WebIDBKey::CreateNumber(primary_key);
   WebIDBKeyPath web_idb_key_path(key_path);
@@ skipping 207 matching lines @@
 
   v8::Local<v8::Value> v8_value = DeserializeIDBValue(
       isolate, scope.GetContext()->Global(), idb_value.Get());
   EXPECT_TRUE(!scope.GetExceptionState().HadException());
   ASSERT_TRUE(v8_value->IsNumber());
   v8::Local<v8::Number> v8_number = v8_value.As<v8::Number>();
   EXPECT_EQ(v8_number->Value(), 42.0);
 }
 
 }  // namespace blink