X87: [compiler] Remove broken support for undetectable strings.

src/full-codegen/x87/full-codegen-x87.cc

Index: src/full-codegen/x87/full-codegen-x87.cc
diff --git a/src/full-codegen/x87/full-codegen-x87.cc b/src/full-codegen/x87/full-codegen-x87.cc
index afd20396e9cb22db578bd856dbd72d80dd700c11..304aee54f403d93965127962d92d1a72bc245fbd 100644
--- a/src/full-codegen/x87/full-codegen-x87.cc
+++ b/src/full-codegen/x87/full-codegen-x87.cc
@@ -4942,11 +4942,7 @@ void FullCodeGenerator::EmitLiteralCompareTypeof(Expression* expr,
   } else if (String::Equals(check, factory->string_string())) {
     __ JumpIfSmi(eax, if_false);
     __ CmpObjectType(eax, FIRST_NONSTRING_TYPE, edx);
-    __ j(above_equal, if_false);
-    // Check for undetectable objects => false.
-    __ test_b(FieldOperand(edx, Map::kBitFieldOffset),
-              1 << Map::kIsUndetectable);
-    Split(zero, if_true, if_false, fall_through);
+    Split(below, if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->symbol_string())) {
     __ JumpIfSmi(eax, if_false);
     __ CmpObjectType(eax, SYMBOL_TYPE, edx);