mac: Don't use |NSHost currentHost|, as it takes 4s per test

sync/util/get_session_name_mac.mm

Index: sync/util/get_session_name_mac.mm
diff --git a/sync/util/get_session_name_mac.mm b/sync/util/get_session_name_mac.mm
index e7d29c46210d264d867ca4db58e28077292b40db..b8eb25e3e94d12f3842699e11211c793f2d7c22c 100644
--- a/sync/util/get_session_name_mac.mm
+++ b/sync/util/get_session_name_mac.mm
@@ -4,23 +4,22 @@
 
 #include "sync/util/get_session_name_mac.h"
 
-#import <Foundation/Foundation.h>
 #import <SystemConfiguration/SCDynamicStoreCopySpecific.h>
-#include <sys/sysctl.h>  // sysctlbyname()
 
-#include "base/mac/foundation_util.h"
-#include "base/mac/mac_util.h"
-#include "base/memory/scoped_nsobject.h"
-#include "base/string_util.h"
-#include "base/sys_info.h"
+#include "base/mac/scoped_cftyperef.h"
 #include "base/sys_string_conversions.h"
 
 namespace syncer {
 namespace internal {
 
 std::string GetHardwareModelName() {
-  NSHost* myHost = [NSHost currentHost];
-  return base::SysNSStringToUTF8([myHost localizedName]);
+  // Do not use NSHost currentHost, as it's very slow. http://crbug.com/138570
+  SCDynamicStoreContext context = { 0, NULL, NULL, NULL };
+  base::mac::ScopedCFTypeRef<SCDynamicStoreRef> store(
+      SCDynamicStoreCreate(kCFAllocatorDefault, CFSTR("policy_subsystem"),
+                           NULL, &context));
+  CFStringRef machine_name = SCDynamicStoreCopyLocalHostName(store.get());
+  return base::SysCFStringRefToUTF8(machine_name);
 }
 
 }  // namespace internal