[ios] Use web_state_list in web_contents_mediator.

ios/clean/chrome/browser/ui/web_contents/web_coordinator.mm

 // Copyright 2016 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/clean/chrome/browser/ui/web_contents/web_coordinator.h"
 
 #include "base/memory/ptr_util.h"
 #import "ios/clean/chrome/browser/ui/context_menu/web_context_menu_coordinator.h"
 #import "ios/clean/chrome/browser/ui/web_contents/web_contents_mediator.h"
 #import "ios/clean/chrome/browser/ui/web_contents/web_contents_view_controller.h"
+#import "ios/shared/chrome/browser/ui/browser_list/browser.h"
 #import "ios/shared/chrome/browser/ui/coordinators/browser_coordinator+internal.h"
 #include "ios/web/public/web_state/web_state.h"
 #import "ios/web/public/web_state/web_state_delegate_bridge.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 @interface WebCoordinator ()<CRWWebStateDelegate> {
   std::unique_ptr<web::WebStateDelegateBridge> _webStateDelegate;
 }
 @property(nonatomic, strong) WebContentsViewController* viewController;
 @property(nonatomic, strong) WebContentsMediator* mediator;
 @end
 
 @implementation WebCoordinator
 @synthesize webState = _webState;
 @synthesize viewController = _viewController;
 @synthesize mediator = _mediator;
 
 - (instancetype)init {
   if ((self = [super init])) {
     _mediator = [[WebContentsMediator alloc] init];
     _webStateDelegate = base::MakeUnique<web::WebStateDelegateBridge>(self);
   }
   return self;
 }
 
 - (void)setWebState:(web::WebState*)webState {
+  // PLACEHOLDER: The web state delegate will be set by another object, and
+  // this coordinator will not need to know the active web state.
   _webState = webState;
   self.webState->SetDelegate(_webStateDelegate.get());
-  self.mediator.webState = self.webState;
 }
 
 - (void)start {
   self.viewController = [[WebContentsViewController alloc] init];
   self.mediator.consumer = self.viewController;
+  self.mediator.webStateList = &self.browser->web_state_list();
   [super start];
 }
 
 - (void)stop {
   [super stop];
-  // PLACEHOLDER: This is how the webUsageEnabled is set to false. Find a
-  // better way in the future.
-  self.mediator.webState = nullptr;
+  [self.mediator disconnect];
 }
 
 - (void)childCoordinatorDidStart:(BrowserCoordinator*)childCoordinator {
   DCHECK([childCoordinator isKindOfClass:[WebContextMenuCoordinator class]]);
   [self.viewController presentViewController:childCoordinator.viewController
                                     animated:YES
                                   completion:nil];
 }
 
 #pragma mark - CRWWebStateDelegate
 
 - (BOOL)webState:(web::WebState*)webState
     handleContextMenu:(const web::ContextMenuParams&)params {
   WebContextMenuCoordinator* contextMenu =
       [[WebContextMenuCoordinator alloc] init];
   [self addChildCoordinator:contextMenu];
   [contextMenu start];
   return YES;
 }
 
 @end