ValueSerializer: add kOneByteString to expected key fast path.

src/value-serializer.cc

 // 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.
 
 #include "src/value-serializer.h"
 
 #include <type_traits>
 
 #include "src/base/logging.h"
 #include "src/conversions.h"
@@ skipping 1243 matching lines @@
     position_ = original_position;
     return false;
   }
 
   expected = String::Flatten(expected);
   DisallowHeapAllocation no_gc;
   String::FlatContent flat = expected->GetFlatContent();
 
   // If the bytes are verbatim what is in the flattened string, then the string
   // is successfully consumed.
-  if (tag == SerializationTag::kUtf8String && flat.IsOneByte()) {
+  if (tag == SerializationTag::kOneByteString && flat.IsOneByte()) {
     Vector<const uint8_t> chars = flat.ToOneByteVector();
     if (byte_length == static_cast<size_t>(chars.length()) &&
-        String::IsAscii(chars.begin(), chars.length()) &&
         memcmp(bytes.begin(), chars.begin(), byte_length) == 0) {
       return true;
     }
   } else if (tag == SerializationTag::kTwoByteString && flat.IsTwoByte()) {
     Vector<const uc16> chars = flat.ToUC16Vector();
     if (byte_length == static_cast<unsigned>(chars.length()) * sizeof(uc16) &&
         memcmp(bytes.begin(), chars.begin(), byte_length) == 0) {
       return true;
     }
+  } else if (tag == SerializationTag::kUtf8String && flat.IsOneByte()) {
+    Vector<const uint8_t> chars = flat.ToOneByteVector();
+    if (byte_length == static_cast<size_t>(chars.length()) &&
+        String::IsAscii(chars.begin(), chars.length()) &&
+        memcmp(bytes.begin(), chars.begin(), byte_length) == 0) {
+      return true;
+    }
   }
 
   position_ = original_position;
   return false;
 }
 
 MaybeHandle<JSObject> ValueDeserializer::ReadJSObject() {
   // If we are at the end of the stack, abort. This function may recurse.
   STACK_CHECK(isolate_, MaybeHandle<JSObject>());
 
@@ skipping 722 matching lines @@
   if (stack.size() != 1) {
     isolate_->Throw(*isolate_->factory()->NewError(
         MessageTemplate::kDataCloneDeserializationError));
     return MaybeHandle<Object>();
   }
   return scope.CloseAndEscape(stack[0]);
 }
 
 }  // namespace internal
 }  // namespace v8