Mark null and undefined as undetectable, and use it to handle abstract equality comparison in the g…

src/crankshaft/arm/lithium-codegen-arm.cc

Index: src/crankshaft/arm/lithium-codegen-arm.cc
diff --git a/src/crankshaft/arm/lithium-codegen-arm.cc b/src/crankshaft/arm/lithium-codegen-arm.cc
index 890220918ac4a99d4cb6b2f435114b29c485216e..8b7c546e88306022b2496b415a9db211a6312674 100644
--- a/src/crankshaft/arm/lithium-codegen-arm.cc
+++ b/src/crankshaft/arm/lithium-codegen-arm.cc
@@ -5241,8 +5241,8 @@ Condition LCodeGen::EmitTypeofIs(Label* true_label,
     final_branch_condition = eq;
 
   } else if (String::Equals(type_name, factory->undefined_string())) {
-    __ CompareRoot(input, Heap::kUndefinedValueRootIndex);
-    __ b(eq, true_label);
+    __ CompareRoot(input, Heap::kNullValueRootIndex);
+    __ b(eq, false_label);
     __ JumpIfSmi(input, false_label);
     // Check for undetectable objects => true.
     __ ldr(scratch, FieldMemOperand(input, HeapObject::kMapOffset));