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

ios/web/test/web_test.mm

Index: ios/web/test/web_test.mm
diff --git a/ios/web/test/web_test.mm b/ios/web/test/web_test.mm
index 26fe6260cdf13c30d8d885e2b8faa3ffe287bc30..5a500f58c59ff79f4562b7d77afc76fe081c8f12 100644
--- a/ios/web/test/web_test.mm
+++ b/ios/web/test/web_test.mm
@@ -71,9 +71,9 @@ void WebTestWithWebController::SetUp() {
   web_state_impl_.reset(new WebStateImpl(GetBrowserState()));
   web_state_impl_->GetNavigationManagerImpl().InitializeSession(nil, nil, NO,
                                                                 0);
+  web_state_impl_->SetWebUsageEnabled(true);
   webController_.reset(web_state_impl_->GetWebController());
 
-  [webController_ setWebUsageEnabled:YES];
   // Force generation of child views; necessary for some tests.
   [webController_ triggerPendingLoad];
   s_html_load_count = 0;
@@ -204,8 +204,8 @@ bool WebTestWithWebController::ResetPageIfNavigationStalled(
   NSString* inner_html = EvaluateJavaScriptAsString(
       @"(document && document.body && document.body.innerHTML) || 'undefined'");
   if ([inner_html rangeOfString:load_check].location == NSNotFound) {
-    [webController_ setWebUsageEnabled:NO];
-    [webController_ setWebUsageEnabled:YES];
+    web_state_impl_->SetWebUsageEnabled(false);
+    web_state_impl_->SetWebUsageEnabled(true);
     [webController_ triggerPendingLoad];
     return true;
   }