Convert Bind to BindRepeating in CastChannelAPI

https://crrev.com/ff530f772caac made explicit that this callback is a
RepeatedCallback. We forgot to change the associated Bind call.

Bug: 1152268
Change-Id: I1b9320ed117a2a2426e8a80ac02ea7ba41901fa7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2595592
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837740}

extensions/browser/api/cast_channel/cast_channel_api.cc

@@ -185,9 +185,10 @@ void CastChannelAPI::OnListenerAdded(const EventListenerInfo& details) {
   if (message_handler_)
     return;
 
-  message_handler_.reset(new CastMessageHandler(
-      base::Bind(&CastChannelAPI::SendEvent, AsWeakPtr(), details.extension_id),
-      cast_socket_service_));
+  message_handler_ = std::make_unique<CastMessageHandler>(
+      base::BindRepeating(&CastChannelAPI::SendEvent, AsWeakPtr(),
+                          details.extension_id),
+      cast_socket_service_);
   cast_socket_service_->task_runner()->PostTask(
       FROM_HERE, base::BindOnce(&CastMessageHandler::Init,
                                 base::Unretained(message_handler_.get())));