Make V8 extras a separate type of native

src/startup-data-util.cc

 // Copyright 2015 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/startup-data-util.h"
 
 #include <stdlib.h>
 #include <string.h>
 
 #include "src/base/logging.h"
@@ skipping 26 matching lines @@
   delete[] natives_.data;
   delete[] snapshot_.data;
 }
 
 
 char* StartupDataHandler::RelativePath(char** buffer, const char* exec_path,
                                        const char* name) {
   DCHECK(exec_path);
   const char* last_slash = strrchr(exec_path, '/');
   if (last_slash) {
-    int after_slash = last_slash - exec_path + 1;
+    int after_slash = static_cast<int>(last_slash - exec_path + 1);
     int name_length = static_cast<int>(strlen(name));
     *buffer = reinterpret_cast<char*>(calloc(after_slash + name_length + 1, 1));
     strncpy(*buffer, exec_path, after_slash);
     strncat(*buffer, name, name_length);
   } else {
     *buffer = strdup(name);
   }
   return *buffer;
 }
 
@@ skipping 10 matching lines @@
                               void (*setter_fn)(v8::StartupData*)) {
   startup_data->data = NULL;
   startup_data->raw_size = 0;
 
   if (!blob_file) return;
 
   FILE* file = fopen(blob_file, "rb");
   if (!file) return;
 
   fseek(file, 0, SEEK_END);
-  startup_data->raw_size = ftell(file);
+  startup_data->raw_size = static_cast<int>(ftell(file));
   rewind(file);
 
   startup_data->data = new char[startup_data->raw_size];
   int read_size = static_cast<int>(fread(const_cast<char*>(startup_data->data),
                                          1, startup_data->raw_size, file));
   fclose(file);
 
   if (startup_data->raw_size == read_size) (*setter_fn)(startup_data);
 }
 
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
 }  // namespace v8