Fix one more cast warning on Win32

src/ia32/macro-assembler-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 630 matching lines @@
   test(instance_type, Immediate(kIsNotStringMask));
   return zero;
 }
 
 
 Condition MacroAssembler::IsObjectNameType(Register heap_object,
                                            Register map,
                                            Register instance_type) {
   mov(map, FieldOperand(heap_object, HeapObject::kMapOffset));
   movzx_b(instance_type, FieldOperand(map, Map::kInstanceTypeOffset));
-  cmpb(instance_type, static_cast<int8_t>(LAST_NAME_TYPE));
+  cmpb(instance_type, static_cast<uint8_t>(LAST_NAME_TYPE));
   return below_equal;
 }
 
 
 void MacroAssembler::IsObjectJSObjectType(Register heap_object,
                                           Register map,
                                           Register scratch,
                                           Label* fail) {
   mov(map, FieldOperand(heap_object, HeapObject::kMapOffset));
   IsInstanceJSObjectType(map, scratch, fail);
@@ skipping 2453 matching lines @@
   j(greater, &no_info_available);
   cmp(MemOperand(scratch_reg, -AllocationSiteInfo::kSize),
       Immediate(Handle<Map>(isolate()->heap()->allocation_site_info_map())));
   bind(&no_info_available);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32