[ios] Added API to enable/disable web usage for WebState.

ios/web/web_state/ui/crw_web_controller_unittest.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/web/web_state/ui/crw_web_controller.h"
 
 #import <WebKit/WebKit.h>
 
 #include <utility>
 
@@ skipping 901 matching lines @@
 
     // Configure web delegate.
     delegate_.reset([[MockInteractionLoader alloc]
         initWithRepresentedObject:
             [OCMockObject niceMockForProtocol:@protocol(CRWWebDelegate)]]);
     ASSERT_TRUE([delegate_ blockPopups]);
     [webController_ setDelegate:delegate_];
 
     // Configure child web state.
     child_web_state_.reset(new web::WebStateImpl(GetBrowserState()));
-    [child_web_state_->GetWebController() setWebUsageEnabled:YES];
+    child_web_state_->SetWebUsageEnabled(true);
     [delegate_ setChildWebController:child_web_state_->GetWebController()];
 
     // Configure child web controller's session controller mock.
     id sessionController =
         [OCMockObject niceMockForClass:[CRWSessionController class]];
     BOOL yes = YES;
     [[[sessionController stub] andReturnValue:OCMOCK_VALUE(yes)] isOpenedByDOM];
     child_web_state_->GetNavigationManagerImpl().SetSessionController(
         sessionController);
 
@@ skipping 122 matching lines @@
 
   [webController_ setDelegate:delegate];
   web::SimulateWKWebViewCrash(webView_);
 
   EXPECT_OCMOCK_VERIFY(delegate);
   EXPECT_FALSE([webController_ isViewAlive]);
   [webController_ setDelegate:nil];
 };
 
 }  // namespace