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

ios/web/web_state/web_state_impl.mm

 // Copyright 2013 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.
 
 #include "ios/web/web_state/web_state_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/strings/sys_string_conversions.h"
@@ skipping 480 matching lines @@
                                           maxBitmapSize:max_bitmap_size
                                               callback:callback];
 }
 
 base::WeakPtr<WebState> WebStateImpl::AsWeakPtr() {
   return weak_factory_.GetWeakPtr();
 }
 
 #pragma mark - WebState implementation
 
+bool WebStateImpl::IsWebUsageEnabled() const {
+  return [web_controller_ webUsageEnabled];
+}
+
+void WebStateImpl::SetWebUsageEnabled(bool enabled) {
+  [web_controller_ setWebUsageEnabled:enabled];
+}
+
 UIView* WebStateImpl::GetView() {
   return [web_controller_ view];
 }
 
 BrowserState* WebStateImpl::GetBrowserState() const {
   return navigation_manager_.GetBrowserState();
 }
 
 void WebStateImpl::OpenURL(const WebState::OpenURLParams& params) {
   DCHECK(Configured());
@@ skipping 107 matching lines @@
     const LoadCommittedDetails& load_details) {
   FOR_EACH_OBSERVER(WebStateObserver, observers_,
                     NavigationItemCommitted(load_details));
 }
 
 WebState* WebStateImpl::GetWebState() {
   return this;
 }
 
 }  // namespace web