Adding utility method to test the version of the OS.

base/ios/device_util.mm

Index: base/ios/device_util.mm
diff --git a/base/ios/device_util.mm b/base/ios/device_util.mm
index 1d16de4b9b878c3890a64dfcd1fee552e789d9ac..8e57d752f9096969ec332a4dcb3470840a257515 100644
--- a/base/ios/device_util.mm
+++ b/base/ios/device_util.mm
@@ -6,6 +6,7 @@
 
 #include <CommonCrypto/CommonDigest.h>
 #import <Foundation/Foundation.h>
+#import <UIKit/UIKit.h>
 
 #include <ifaddrs.h>
 #include <net/if_dl.h>
@@ -16,6 +17,7 @@
 #include "base/logging.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
+#include "base/sys_info.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/sys_string_conversions.h"
@@ -103,7 +105,10 @@ std::string GetDeviceIdentifier(const char* salt) {
   NSString* client_id = [defaults stringForKey:kClientIdPreferenceKey];
 
   if (!client_id) {
-    client_id = base::SysUTF8ToNSString(GetRandomId());
+    if (base::SysInfo::IsRunningOnIOS6OrLater())
+      client_id = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
+    else
+      client_id = base::SysUTF8ToNSString(GetRandomId());
     [defaults setObject:client_id forKey:kClientIdPreferenceKey];
     [defaults synchronize];
   }