Fix crash in StaticHTMLNativeContent when deallocating WKWebView on iOS9

ios/chrome/browser/ui/browser_view_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/browser_view_controller.h"
 
 #import <AssetsLibrary/AssetsLibrary.h>
 #import <MobileCoreServices/MobileCoreServices.h>
 #import <PassKit/PassKit.h>
 #import <Photos/Photos.h>
@@ skipping 2732 matching lines @@
   return _voiceSearchBar;
 }
 
 #pragma mark - Install OverScrollActionController method.
 - (void)setOverScrollActionControllerToStaticNativeContent:
     (StaticHtmlNativeContent*)nativeContent {
   if (!IsIPadIdiom() && !FirstRun::IsChromeFirstRun()) {
     OverscrollActionsController* controller =
         [[[OverscrollActionsController alloc]
             initWithScrollView:[nativeContent scrollView]] autorelease];
-    [[nativeContent scrollView] setDelegate:controller];
     [controller setDelegate:self];
     OverscrollStyle style = _isOffTheRecord
                                 ? OverscrollStyle::REGULAR_PAGE_INCOGNITO
                                 : OverscrollStyle::REGULAR_PAGE_NON_INCOGNITO;
     controller.style = style;
     nativeContent.overscrollActionsController = controller;
   }
 }
 
 #pragma mark - OverscrollActionsControllerDelegate methods.
@@ skipping 2333 matching lines @@
 
 - (UIView*)voiceSearchButton {
   return _voiceSearchButton;
 }
 
 - (id<LogoAnimationControllerOwner>)logoAnimationControllerOwner {
   return [self currentLogoAnimationControllerOwner];
 }
 
 @end