[compiler] Remove broken support for undetectable strings.

src/full-codegen/arm/full-codegen-arm.cc

Index: src/full-codegen/arm/full-codegen-arm.cc
diff --git a/src/full-codegen/arm/full-codegen-arm.cc b/src/full-codegen/arm/full-codegen-arm.cc
index b1903a6a7fcb807efea088b8f469633560911d72..201bb89ddccf5bc2d8f3a23d60dae5b81e132b6a 100644
--- a/src/full-codegen/arm/full-codegen-arm.cc
+++ b/src/full-codegen/arm/full-codegen-arm.cc
@@ -5032,12 +5032,8 @@ void FullCodeGenerator::EmitLiteralCompareTypeof(Expression* expr,
     Split(eq, if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->string_string())) {
     __ JumpIfSmi(r0, if_false);
-    // Check for undetectable objects => false.
     __ CompareObjectType(r0, r0, r1, FIRST_NONSTRING_TYPE);
-    __ b(ge, if_false);
-    __ ldrb(r1, FieldMemOperand(r0, Map::kBitFieldOffset));
-    __ tst(r1, Operand(1 << Map::kIsUndetectable));
-    Split(eq, if_true, if_false, fall_through);
+    Split(lt, if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->symbol_string())) {
     __ JumpIfSmi(r0, if_false);
     __ CompareObjectType(r0, r0, r1, SYMBOL_TYPE);