Adding utility method to test the version of the OS.

base/ios/device_util.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/ios/device_util.h"
 
 #include <CommonCrypto/CommonDigest.h>
-#import <Foundation/Foundation.h>
+#import <UIKit/UIKit.h>
 
 #include <ifaddrs.h>
 #include <net/if_dl.h>
 #include <string.h>
 #include <sys/socket.h>
 #include <sys/sysctl.h>
 
+#include "base/ios/ios_util.h"
 #include "base/logging.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/sys_string_conversions.h"
 
 namespace {
 
 // Client ID key in the user preferences.
@@ skipping 70 matching lines @@
   base::mac::ScopedCFTypeRef<CFStringRef> uuid_string(
       CFUUIDCreateString(kCFAllocatorDefault, uuid_object));
   return base::SysCFStringRefToUTF8(uuid_string);
 }
 
 std::string GetDeviceIdentifier(const char* salt) {
   NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
   NSString* client_id = [defaults stringForKey:kClientIdPreferenceKey];
 
   if (!client_id) {
-    client_id = base::SysUTF8ToNSString(GetRandomId());
+    if (base::ios::IsRunningOnIOS6OrLater())
+      client_id = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
+    else
+      client_id = base::SysUTF8ToNSString(GetRandomId());
     [defaults setObject:client_id forKey:kClientIdPreferenceKey];
     [defaults synchronize];
   }
 
   NSData* hash_data = [[NSString stringWithFormat:@"%@%s", client_id,
       salt ? salt : kDefaultSalt] dataUsingEncoding:NSUTF8StringEncoding];
 
   unsigned char hash[CC_SHA256_DIGEST_LENGTH];
   CC_SHA256([hash_data bytes], [hash_data length], hash);
   CFUUIDBytes* uuid_bytes = reinterpret_cast<CFUUIDBytes*>(hash);
 
   base::mac::ScopedCFTypeRef<CFUUIDRef>
       uuid_object(CFUUIDCreateFromUUIDBytes(kCFAllocatorDefault, *uuid_bytes));
   base::mac::ScopedCFTypeRef<CFStringRef> device_id(
       CFUUIDCreateString(kCFAllocatorDefault, uuid_object));
   return base::SysCFStringRefToUTF8(device_id);
 }
 
 }  // namespace device_util
 }  // namespace ios