Add a missing cast to ValueDeserializer::ReadVarint.

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 802 matching lines @@
   // See also https://developers.google.com/protocol-buffers/docs/encoding
   static_assert(std::is_integral<T>::value && std::is_unsigned<T>::value,
                 "Only unsigned integer types can be read as varints.");
   T value = 0;
   unsigned shift = 0;
   bool has_another_byte;
   do {
     if (position_ >= end_) return Nothing<T>();
     uint8_t byte = *position_;
     if (V8_LIKELY(shift < sizeof(T) * 8)) {
-      value |= (byte & 0x7f) << shift;
+      value |= static_cast<T>(byte & 0x7f) << shift;
       shift += 7;
     }
     has_another_byte = byte & 0x80;
     position_++;
   } while (has_another_byte);
   return Just(value);
 }
 
 template <typename T>
 Maybe<T> ValueDeserializer::ReadZigZag() {
@@ skipping 645 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