Removed CRWWebController dependency from NativeAppNavigationController.

ios/chrome/browser/tabs/tab.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/tabs/tab.h"
 
 #import <CoreLocation/CoreLocation.h>
 #import <UIKit/UIKit.h>
 
 #include <utility>
@@ skipping 2181 matching lines @@
 }
 
 - (void)initNativeAppNavigationController {
   if (browserState_->IsOffTheRecord())
     return;
   DCHECK(!nativeAppNavigationController_);
   nativeAppNavigationController_.reset([[NativeAppNavigationController alloc]
           initWithWebState:self.webState
       requestContextGetter:browserState_->GetRequestContext()
                        tab:self]);
-  [self.webController addObserver:nativeAppNavigationController_];
   DCHECK(nativeAppNavigationController_);
 }
 
 - (id<PassKitDialogProvider>)passKitDialogProvider {
   return passKitDialogProvider_.get();
 }
 
 - (void)setPassKitDialogProvider:(id<PassKitDialogProvider>)provider {
   passKitDialogProvider_.reset(provider);
 }
@@ skipping 24 matching lines @@
 
 - (TabModel*)parentTabModel {
   return parentTabModel_;
 }
 
 - (FormInputAccessoryViewController*)inputAccessoryViewController {
   return inputAccessoryViewController_.get();
 }
 
 @end