Reverted !client_id check because it caused unit test failure.

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 <UIKit/UIKit.h>
 
 #include <ifaddrs.h>
@@ skipping 28 matching lines @@
 
   // Try to migrate from legacy client id.
   NSString* client_id = [defaults stringForKey:kLegacyClientIdPreferenceKey];
 
   // Some iOS6 devices return a buggy identifierForVendor:
   // http://openradar.appspot.com/12377282. If this is the case, revert to
   // generating a new one.
   if (!client_id || [client_id isEqualToString:kZeroUUID]) {
     if (base::ios::IsRunningOnIOS6OrLater()) {
       client_id = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
-      if (!client_id || [client_id isEqualToString:kZeroUUID])
+      if ([client_id isEqualToString:kZeroUUID])
         client_id = base::SysUTF8ToNSString(ios::device_util::GetRandomId());
     } else {
       client_id = base::SysUTF8ToNSString(ios::device_util::GetRandomId());
     }
   }
   return client_id;
 }
 
 }  // namespace
 
@@ skipping 96 matching lines @@
     [defaults setObject:current_hardware forKey:kHardwareTypePreferenceKey];
     [defaults synchronize];
   }
 
   return GetSaltedString(base::SysNSStringToUTF8(client_id),
                          salt ? salt : kDefaultSalt);
 }
 
 std::string GetSaltedString(const std::string& in_string,
                             const std::string& salt) {
-  DCHECK(in_string.length());
   DCHECK(salt.length());
   NSData* hash_data = [base::SysUTF8ToNSString(in_string + salt)
       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::ScopedCFTypeRef<CFUUIDRef> uuid_object(
       CFUUIDCreateFromUUIDBytes(kCFAllocatorDefault, *uuid_bytes));
   base::ScopedCFTypeRef<CFStringRef> device_id(
       CFUUIDCreateString(kCFAllocatorDefault, uuid_object));
   return base::SysCFStringRefToUTF8(device_id);
 }
 
 }  // namespace device_util
 }  // namespace ios