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

src/crankshaft/x87/lithium-codegen-x87.cc

Index: src/crankshaft/x87/lithium-codegen-x87.cc
diff --git a/src/crankshaft/x87/lithium-codegen-x87.cc b/src/crankshaft/x87/lithium-codegen-x87.cc
index 8c10d119a5c76b936595f24163c7a902ee8b1a58..543b90b0863cd06ca28c8c2c603400acf0db3ebc 100644
--- a/src/crankshaft/x87/lithium-codegen-x87.cc
+++ b/src/crankshaft/x87/lithium-codegen-x87.cc
@@ -5687,8 +5687,8 @@ Condition LCodeGen::EmitTypeofIs(LTypeofIsAndBranch* instr, Register input) {
     final_branch_condition = equal;
 
   } else if (String::Equals(type_name, factory()->undefined_string())) {
-    __ cmp(input, factory()->undefined_value());
-    __ j(equal, true_label, true_distance);
+    __ cmp(input, factory()->null_value());
+    __ j(equal, false_label, false_distance);
     __ JumpIfSmi(input, false_label, false_distance);
     // Check for undetectable objects => true.
     __ mov(input, FieldOperand(input, HeapObject::kMapOffset));