[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"
 
 #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/coordinator_context/coordinator_context.h"
-#import "ios/shared/chrome/browser/ui/coordinators/browser_coordinator+internal.h"
+#import "ios/shared/chrome/browser/tabs/web_state_list.h"
+#import "ios/shared/chrome/browser/ui/browser_list/browser.h"
 #include "ios/web/public/web_state/web_state.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 @interface WebCoordinator ()
 @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];
-  }
-  return self;
-}
-
-- (void)setWebState:(web::WebState*)webState {
-  _webState = webState;
-  self.mediator.webState = self.webState;
-}
-
 - (void)start {
   self.viewController = [[WebContentsViewController alloc] init];
+  self.mediator = [[WebContentsMediator alloc] init];
+  self.mediator.webStateList = &self.browser->web_state_list();
   self.mediator.consumer = self.viewController;
 
   // Reminder: this is a no-op if |baseViewController| is nil, for example
   // when this coordinator's view controller will be contained instead of
   // presented.
   [self.context.baseViewController presentViewController:self.viewController
                                                 animated:self.context.animated
                                               completion:nil];
   [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;
+  web::WebState* webState = self.browser->web_state_list().GetActiveWebState();

[lpromero, 2017/04/03 09:48:36]

I'd move this to the WebContentsMediator and here in the stop method I'd release
the mediator:

self.mediator = nil;
self.viewController = nil;

[edchin, 2017/04/04 19:50:12]

I added a -disconnect method. PTAL. 

+  if (webState) {
+    webState->SetWebUsageEnabled(false);
+  }
 }
 
 @end