Fix memory leak reported by clang static analyzer.

ios/chrome/browser/ui/elements/selector_coordinator.mm

 // Copyright 2016 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/elements/selector_coordinator.h"
 
 #import "base/mac/objc_property_releaser.h"
 #import "ios/chrome/browser/ui/elements/selector_picker_view_controller.h"
 #import "ios/chrome/browser/ui/elements/selector_picker_presentation_controller.h"
 #import "ios/chrome/browser/ui/elements/selector_view_controller_delegate.h"
@@ skipping 22 matching lines @@
     (nullable UIViewController*)viewController {
   self = [super initWithBaseViewController:viewController];
   if (self) {
     _propertyReleaser_SelectorCoordinator.Init(self,
                                                [SelectorCoordinator class]);
   }
   return self;
 }
 
 - (void)start {
-  self.selectorPickerViewController =
-      [[SelectorPickerViewController alloc] initWithOptions:self.options
-                                                    default:self.defaultOption];
+  self.selectorPickerViewController = [[[SelectorPickerViewController alloc]
+      initWithOptions:self.options
+              default:self.defaultOption] autorelease];
   self.selectorPickerViewController.delegate = self;
 
   self.selectorPickerViewController.modalTransitionStyle =
       UIModalTransitionStyleCoverVertical;
   self.selectorPickerViewController.modalPresentationStyle =
       UIModalPresentationCustom;
   self.selectorPickerViewController.transitioningDelegate = self;
 
   [self.baseViewController
       presentViewController:self.selectorPickerViewController
@@ skipping 18 matching lines @@
 
 - (UIPresentationController*)
 presentationControllerForPresentedViewController:(UIViewController*)presented
                         presentingViewController:(UIViewController*)presenting
                             sourceViewController:(UIViewController*)source {
   return [[[SelectorPickerPresentationController alloc]
       initWithPresentedViewController:self.selectorPickerViewController
              presentingViewController:self.baseViewController] autorelease];
 }
 
-@end
+@end