Implement Harmony semantics for typeof null (behind a flag).

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
diff --git a/src/arm/full-codegen-arm.cc b/src/arm/full-codegen-arm.cc
index cdfc0a9acf5cf3813bc42e9225defd0fce7c6b3e..3742d166ca3c23d73e5aad033406e454c2a0bca4 100644
--- a/src/arm/full-codegen-arm.cc
+++ b/src/arm/full-codegen-arm.cc
@@ -4030,6 +4030,10 @@ void FullCodeGenerator::EmitLiteralCompareTypeof(Expression* expr,
     __ b(eq, if_true);
     __ CompareRoot(r0, Heap::kFalseValueRootIndex);
     Split(eq, if_true, if_false, fall_through);
+  } else if (FLAG_harmony_typeof &&
+             check->Equals(isolate()->heap()->null_symbol())) {
+    __ CompareRoot(r0, Heap::kNullValueRootIndex);
+    Split(eq, if_true, if_false, fall_through);
   } else if (check->Equals(isolate()->heap()->undefined_symbol())) {
     __ CompareRoot(r0, Heap::kUndefinedValueRootIndex);
     __ b(eq, if_true);
@@ -4047,8 +4051,10 @@ void FullCodeGenerator::EmitLiteralCompareTypeof(Expression* expr,
 
   } else if (check->Equals(isolate()->heap()->object_symbol())) {
     __ JumpIfSmi(r0, if_false);
-    __ CompareRoot(r0, Heap::kNullValueRootIndex);
-    __ b(eq, if_true);
+    if (!FLAG_harmony_typeof) {
+      __ CompareRoot(r0, Heap::kNullValueRootIndex);
+      __ b(eq, if_true);
+    }
     // Check for JS objects => true.
     __ CompareObjectType(r0, r0, r1, FIRST_NONCALLABLE_SPEC_OBJECT_TYPE);
     __ b(lt, if_false);