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

ios/web/web_state/web_state_impl.mm

Index: ios/web/web_state/web_state_impl.mm
diff --git a/ios/web/web_state/web_state_impl.mm b/ios/web/web_state/web_state_impl.mm
index 2bce17ae9a1e6cb1abbeb68ec45247b0de405600..09ca232373b4bde6179cf9590e7373fc34ac1679 100644
--- a/ios/web/web_state/web_state_impl.mm
+++ b/ios/web/web_state/web_state_impl.mm
@@ -498,6 +498,14 @@ base::WeakPtr<WebState> WebStateImpl::AsWeakPtr() {
 
 #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];
 }