Also fix cast warnings on Win64

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/12398011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13816 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/code-stubs-x64.cc

@@ -6261,7 +6261,7 @@ void NameDictionaryLookupStub::GenerateNegativeLookup(MacroAssembler* masm,
              Immediate(kIsInternalizedMask));
     __ j(not_zero, &good, Label::kNear);
     __ cmpb(FieldOperand(entity_name, Map::kInstanceTypeOffset),
-            Immediate(static_cast<int8_t>(SYMBOL_TYPE)));
+            Immediate(static_cast<uint8_t>(SYMBOL_TYPE)));
     __ j(not_equal, miss);
 
     __ bind(&good);
@@ -6395,7 +6395,7 @@ void NameDictionaryLookupStub::Generate(MacroAssembler* masm) {
                Immediate(kIsInternalizedMask));
       __ j(not_zero, &cont);
       __ cmpb(FieldOperand(scratch, Map::kInstanceTypeOffset),
-              Immediate(static_cast<int8_t>(SYMBOL_TYPE)));
+              Immediate(static_cast<uint8_t>(SYMBOL_TYPE)));
       __ j(not_equal, &maybe_in_dictionary);
       __ bind(&cont);
     }

src/x64/macro-assembler-x64.cc

@@ -3059,7 +3059,7 @@ Condition MacroAssembler::IsObjectNameType(Register heap_object,
                                            Register instance_type) {
   movq(map, FieldOperand(heap_object, HeapObject::kMapOffset));
   movzxbl(instance_type, FieldOperand(map, Map::kInstanceTypeOffset));
-  cmpb(instance_type, Immediate(static_cast<int8_t>(LAST_NAME_TYPE)));
+  cmpb(instance_type, Immediate(static_cast<uint8_t>(LAST_NAME_TYPE)));
   return below_equal;
 }