Disable code coverage for systemlib.hhas

It has no line number information.

hphp/runtime/vm/bytecode.cpp

@@ -7186,7 +7186,8 @@ void VMExecutionContext::recordCodeCoverage(PC pc) {
   Unit* unit = getFP()->m_func->unit();
   assert(unit != nullptr);
   if (unit == SystemLib::s_nativeFuncUnit ||
-      unit == SystemLib::s_nativeClassUnit) {
+      unit == SystemLib::s_nativeClassUnit ||
+      unit == SystemLib::s_hhas_unit) {
     return;
   }
   int line = unit->getLineNumber(pcOff());

hphp/test/slow/code_coverage/hhas_coverage.php

@@ -0,0 +1,9 @@
+<?php
+
+function test($a) {
+  fb_enable_code_coverage();
+  var_dump(array_map(null, $a));
+  fb_disable_code_coverage();
+}
+
+test(array(1,2,3));

hphp/test/slow/code_coverage/hhas_coverage.php.expect

@@ -0,0 +1,8 @@
+array(3) {
+  [0]=>
+  int(1)
+  [1]=>
+  int(2)
+  [2]=>
+  int(3)
+}