Follow up from ARC conversion

ios/chrome/browser/ui/toolbar/web_toolbar_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/chrome/browser/ui/toolbar/web_toolbar_controller.h"
 
 #import <CoreLocation/CoreLocation.h>
 #include <QuartzCore/QuartzCore.h>
 
 #include <stdint.h>
@@ skipping 831 matching lines @@
   [_tabHistoryPopupController fadeInPopupFromSource:convertedOrigin
                                       toDestination:destination];
   [[NSNotificationCenter defaultCenter]
       postNotificationName:kTabHistoryPopupWillShowNotification
                     object:nil];
 }
 
 - (void)dismissTabHistoryPopup {
   if (!_tabHistoryPopupController)
     return;
-  TabHistoryPopupController* tempTHPC = _tabHistoryPopupController;
+  __block TabHistoryPopupController* tempTHPC = _tabHistoryPopupController;
   [tempTHPC containerView].userInteractionEnabled = NO;
   [tempTHPC dismissAnimatedWithCompletion:^{
     // Unpress the back/forward button by restoring the normal and
     // highlighted images to their usual state.
     [self setImagesForNavButton:_backButton withTabHistoryVisible:NO];
     [self setImagesForNavButton:_forwardButton withTabHistoryVisible:NO];
     // Reference tempTHPC so the block retains it.
-    [tempTHPC self];
+    tempTHPC = nil;
   }];
   // reset _tabHistoryPopupController to prevent -applicationDidEnterBackground
   // from posting another kTabHistoryPopupWillHideNotification.
   _tabHistoryPopupController = nil;
 
   [[NSNotificationCenter defaultCenter]
       postNotificationName:kTabHistoryPopupWillHideNotification
                     object:nil];
 }
 
@@ skipping 1700 matching lines @@
 
 - (BOOL)isPrerenderAnimationRunning {
   return _prerenderAnimating;
 }
 
 - (OmniboxTextFieldIOS*)omnibox {
   return _omniBox;
 }
 
 @end