Fix crash in StaticHTMLNativeContent when deallocating WKWebView on iOS9

ios/chrome/browser/ui/static_content/static_html_native_content.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/static_content/static_html_native_content.h"
 
 #include "base/logging.h"
 #import "base/mac/scoped_nsobject.h"
 #import "ios/chrome/browser/ui/overscroll_actions/overscroll_actions_controller.h"
 #include "ios/chrome/browser/ui/static_content/static_html_view_controller.h"
@@ skipping 50 matching lines @@
   DCHECK(URL.is_valid());
   DCHECK(resourcePath);
   base::scoped_nsobject<StaticHtmlViewController> HTMLViewController(
       [[StaticHtmlViewController alloc] initWithResource:resourcePath
                                             browserState:browserState]);
   return [self initWithLoader:loader
       staticHTMLViewController:HTMLViewController
                            URL:URL];
 }
 
+- (void)dealloc {
+  [[self scrollView] setDelegate:nil];
+  [super dealloc];
+}
+
 - (void)loadURL:(const GURL&)URL
              referrer:(const web::Referrer&)referrer
            transition:(ui::PageTransition)transition
     rendererInitiated:(BOOL)rendererInitiated {
   [_loader loadURL:URL
                referrer:referrer
              transition:transition
       rendererInitiated:rendererInitiated];
 }
 
 - (OverscrollActionsController*)overscrollActionsController {
   return _overscrollActionsController.get();
 }
 
 - (void)setOverscrollActionsController:
     (OverscrollActionsController*)controller {
   _overscrollActionsController.reset([controller retain]);
+  [[self scrollView] setDelegate:controller];
 }
 
 #pragma mark -
 #pragma mark CRWNativeContent implementation
 
 - (void)close {
   [_overscrollActionsController invalidate];
 }
 
 - (void)willUpdateSnapshot {
@@ skipping 44 matching lines @@
   if (!_webUsageEnabled) {
     _staticHTMLViewController.reset();
   }
 }
 
 - (UIScrollView*)scrollView {
   return [_staticHTMLViewController scrollView];
 }
 
 @end