Fix memory leak reported by clang static analyzer.

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

Index: ios/chrome/browser/ui/elements/selector_coordinator.mm
diff --git a/ios/chrome/browser/ui/elements/selector_coordinator.mm b/ios/chrome/browser/ui/elements/selector_coordinator.mm
index 155daeedaac90aa89b6e4409fff18f0751d62926..8a90f0492c3c059186e2482dd2bc1cab655eb9c7 100644
--- a/ios/chrome/browser/ui/elements/selector_coordinator.mm
+++ b/ios/chrome/browser/ui/elements/selector_coordinator.mm
@@ -40,9 +40,9 @@
 }
 
 - (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 =
@@ -81,4 +81,4 @@ presentationControllerForPresentedViewController:(UIViewController*)presented
              presentingViewController:self.baseViewController] autorelease];
 }
 
-@end
+@end