[parser, serializer] Fix more -Wsign-compare warnings.

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 1712 matching lines @@
         JSObject::DefineOwnPropertyIgnoreAttributes(&it, value, NONE)
             .is_null()) {
       return Nothing<bool>();
     }
   }
   return Just(true);
 }
 
 MaybeHandle<Object>
 ValueDeserializer::ReadObjectUsingEntireBufferForLegacyFormat() {
-  DCHECK_EQ(version_, 0);
+  DCHECK_EQ(version_, 0u);
   HandleScope scope(isolate_);
   std::vector<Handle<Object>> stack;
   while (position_ < end_) {
     SerializationTag tag;
     if (!PeekTag().To(&tag)) break;
 
     Handle<Object> new_object;
     switch (tag) {
       case SerializationTag::kEndJSObject: {
         ConsumeTag(SerializationTag::kEndJSObject);
@@ skipping 81 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