Fix a memory leak found by clang static analyzer.

ios/web/navigation/crw_session_controller.mm

 // Copyright 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.
 
 #import "ios/web/navigation/crw_session_controller.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <utility>
@@ skipping 825 matching lines @@
   else
     _useDesktopUserAgentForNextPendingEntry = YES;
 }
 
 #pragma mark -
 #pragma mark Private methods
 
 - (NSString*)uniqueID {
   CFUUIDRef uuidRef = CFUUIDCreate(NULL);
   CFStringRef uuidStringRef = CFUUIDCreateString(NULL, uuidRef);
+  CFRelease(uuidRef);

[Eugene But (OOO till 7-30), 2016/09/20 21:59:40]

How about simply: |return [NSUUID NSUUID].UUIDString;|

[sdefresne, 2016/09/21 09:19:08]

I'll leave this to you as owners of the code to decide whether you want to
rewrite it from using CoreFoundation to using NS objects.

+
   NSString* uuid =
       [NSString stringWithString:base::mac::ObjCCastStrict<NSString>(
                                      CFBridgingRelease(uuidStringRef))];
   return uuid;
 }
 
 - (CRWSessionEntry*)sessionEntryWithURL:(const GURL&)url
                                referrer:(const web::Referrer&)referrer
                              transition:(ui::PageTransition)transition
                     useDesktopUserAgent:(BOOL)useDesktopUserAgent
@@ skipping 15 matching lines @@
   std::unique_ptr<web::NavigationItemImpl> item(new web::NavigationItemImpl());
   item->SetURL(loaded_url);
   item->SetReferrer(referrer);
   item->SetTransitionType(transition);
   item->SetIsOverridingUserAgent(useDesktopUserAgent);
   item->set_is_renderer_initiated(rendererInitiated);
   return [[CRWSessionEntry alloc] initWithNavigationItem:std::move(item)];
 }
 
 @end