[compiler] Remove broken support for undetectable strings.

src/arm64/lithium-codegen-arm64.cc

Index: src/arm64/lithium-codegen-arm64.cc
diff --git a/src/arm64/lithium-codegen-arm64.cc b/src/arm64/lithium-codegen-arm64.cc
index b1a0b44c0ce41b3620d92c5bb67d1d0ffa7a5b90..17ea0feeffd743015110f0df1642c2aa1a5e78b0 100644
--- a/src/arm64/lithium-codegen-arm64.cc
+++ b/src/arm64/lithium-codegen-arm64.cc
@@ -5939,10 +5939,8 @@ void LCodeGen::DoTypeofIsAndBranch(LTypeofIsAndBranch* instr) {
     Register scratch = ToRegister(instr->temp2());
 
     __ JumpIfSmi(value, false_label);
-    __ JumpIfObjectType(
-        value, map, scratch, FIRST_NONSTRING_TYPE, false_label, ge);
-    __ Ldrb(scratch, FieldMemOperand(map, Map::kBitFieldOffset));
-    EmitTestAndBranch(instr, eq, scratch, 1 << Map::kIsUndetectable);
+    __ CompareObjectType(value, map, scratch, FIRST_NONSTRING_TYPE);
+    EmitBranch(instr, lt);
 
   } else if (String::Equals(type_name, factory->symbol_string())) {
     DCHECK((instr->temp1() != NULL) && (instr->temp2() != NULL));