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

src/crankshaft/x64/lithium-codegen-x64.cc

Index: src/crankshaft/x64/lithium-codegen-x64.cc
diff --git a/src/crankshaft/x64/lithium-codegen-x64.cc b/src/crankshaft/x64/lithium-codegen-x64.cc
index a9c634336876526416862eaea16d8d997e6090f5..b289cf9c7df876f37241ecbe5cd0116dc36a26fb 100644
--- a/src/crankshaft/x64/lithium-codegen-x64.cc
+++ b/src/crankshaft/x64/lithium-codegen-x64.cc
@@ -5319,8 +5319,8 @@ Condition LCodeGen::EmitTypeofIs(LTypeofIsAndBranch* instr, Register input) {
     final_branch_condition = equal;
 
   } else if (String::Equals(type_name, factory->undefined_string())) {
-    __ CompareRoot(input, Heap::kUndefinedValueRootIndex);
-    __ j(equal, true_label, true_distance);
+    __ CompareRoot(input, Heap::kNullValueRootIndex);
+    __ j(equal, false_label, false_distance);
     __ JumpIfSmi(input, false_label, false_distance);
     // Check for undetectable objects => true.
     __ movp(input, FieldOperand(input, HeapObject::kMapOffset));