[clang] Use -Wshorten-64-to-32 to enable warnings about 64bit to 32bit truncations.

src/snapshot/mksnapshot.cc

 // Copyright 2006-2008 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 <errno.h>
 #include <signal.h>
 #include <stdio.h>
 
 #include "src/v8.h"
 
@@ skipping 100 matching lines @@
 
 char* GetExtraCode(char* filename) {
   if (filename == NULL || strlen(filename) == 0) return NULL;
   ::printf("Embedding extra script: %s\n", filename);
   FILE* file = base::OS::FOpen(filename, "rb");
   if (file == NULL) {
     fprintf(stderr, "Failed to open '%s': errno %d\n", filename, errno);
     exit(1);
   }
   fseek(file, 0, SEEK_END);
-  int size = ftell(file);
+  size_t size = ftell(file);
   rewind(file);
   char* chars = new char[size + 1];
   chars[size] = '\0';
-  for (int i = 0; i < size;) {
-    int read = static_cast<int>(fread(&chars[i], 1, size - i, file));
-    if (read < 0) {
+  for (size_t i = 0; i < size;) {
+    size_t read = fread(&chars[i], 1, size - i, file);
+    if (ferror(file)) {
       fprintf(stderr, "Failed to read '%s': errno %d\n", filename, errno);
       exit(1);
     }
     i += read;
   }
   fclose(file);
   return chars;
 }
 
 
@@ skipping 26 matching lines @@
     writer.WriteSnapshot(blob);
     delete[] extra_code;
     delete[] blob.data;
   }
 
   V8::Dispose();
   V8::ShutdownPlatform();
   delete platform;
   return 0;
 }