Fix ARM regression introduced with polymorphic array support.

BUG=none
TEST=Kraken on ARM

Review URL: http://codereview.chromium.org/7218068

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8484 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/macro-assembler-arm.cc

@@ -1666,7 +1666,7 @@ void MacroAssembler::CheckFastElements(Register map,
                                        Register scratch,
                                        Label* fail) {
   STATIC_ASSERT(JSObject::FAST_ELEMENTS == 0);
-  ldrb(scratch, FieldMemOperand(map, Map::kInstanceTypeOffset));
+  ldrb(scratch, FieldMemOperand(map, Map::kBitField2Offset));
   cmp(scratch, Operand(Map::kMaximumBitField2FastElementValue));
   b(hi, fail);
 }