[Mac] Add a perf test that counts the number of Mach ports in the browser.

base/mach_ipc_mac.mm

Index: base/mach_ipc_mac.mm
diff --git a/base/mach_ipc_mac.mm b/base/mach_ipc_mac.mm
index b6dedd2b89190b7cea5dba167105c77db155e818..61ea4e333e78e3f58f29d572a1c8284cdeda331a 100644
--- a/base/mach_ipc_mac.mm
+++ b/base/mach_ipc_mac.mm
@@ -5,6 +5,7 @@
 #include "base/mach_ipc_mac.h"
 
 #import <Foundation/Foundation.h>
+#include <mach/vm_map.h>
 
 #include <stdio.h>
 #include "base/logging.h"
@@ -322,4 +323,36 @@ kern_return_t MachPortSender::SendMessage(MachSendMessage &message,
   return result;
 }
 
+//==============================================================================
+
+namespace mac {
+
+kern_return_t GetNumberOfMachPorts(mach_port_t task_port, int* num_ports) {
+  mach_port_name_array_t names;
+  mach_msg_type_number_t names_count;
+  mach_port_type_array_t types;
+  mach_msg_type_number_t types_count;
+
+  // A friendlier interface would allow NULL buffers to only get the counts.
+  kern_return_t kr = mach_port_names(task_port, &names, &names_count,
+                                     &types, &types_count);
+  if (kr != KERN_SUCCESS)
+    return kr;
+
+  // The documentation states this is an invariant.
+  DCHECK_EQ(names_count, types_count);
+  *num_ports = names_count;
+
+  kr = vm_deallocate(mach_task_self(),
+      reinterpret_cast<vm_address_t>(names),
+      names_count * sizeof(mach_port_name_array_t));
+  kr = vm_deallocate(mach_task_self(),
+      reinterpret_cast<vm_address_t>(types),
+      types_count * sizeof(mach_port_type_array_t));
+
+  return kr;
+}
+
+}  // namespace mac
+
 }  // namespace base