Enable -Wundeclared-selector on ios.

ios/web/web_state/ui/crw_web_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/web_state/ui/crw_web_controller.h"
 
 #import <WebKit/WebKit.h>
 
 #import <objc/runtime.h>
 #include <stddef.h>
@@ skipping 3960 matching lines @@
     // so that the delegate can return something immediately for the default
     // overlay image.
     _placeholderOverlayView.get().image = [[self class] defaultSnapshotImage];
   }
 }
 
 - (void)removePlaceholderOverlay {
   if (!_placeholderOverlayView || _overlayPreviewMode)
     return;
 
-  [NSObject cancelPreviousPerformRequestsWithTarget:self
-                                           selector:@selector(removeOverlay)
-                                             object:nil];
+  [NSObject
+      cancelPreviousPerformRequestsWithTarget:self
+                                     selector:@selector(
+                                                  removePlaceholderOverlay)
+                                       object:nil];
   // Remove overlay with transition.
   [UIView animateWithDuration:kSnapshotOverlayTransition
       animations:^{
         [_placeholderOverlayView setAlpha:0.0f];
       }
       completion:^(BOOL finished) {
         [_placeholderOverlayView removeFromSuperview];
         _placeholderOverlayView.reset();
       }];
 }
@@ skipping 1790 matching lines @@
   }
 
   return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
 }
 
 - (NSString*)refererFromNavigationAction:(WKNavigationAction*)action {
   return [action.request valueForHTTPHeaderField:@"Referer"];
 }
 
 @end