Convert base::CancelableCallback in media::WebMediaPlayerImpl

WebMediaPlayerImpl uses a base::CancelableCallback to hold the callback
that will receive a routing token for the Android overlay. The callback
is canceled if DisableOverlay is called before the token is received.

The type of this callback should be media::RoutingTokenCallback which is
a base::OnceCallback, so we'll switch to base::CancelableOnceCallback.

BUG=1102651

Change-Id: I50845dba9be97f30b86f8ebb71a152457ff3df7a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2284208Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#786446}

media/blink/webmediaplayer_impl.cc

@@ -582,7 +582,7 @@ void WebMediaPlayerImpl::EnableOverlay() {
       overlay_mode_ == OverlayMode::kUseAndroidOverlay) {
     overlay_routing_token_is_pending_ = true;
     token_available_cb_.Reset(
-        base::Bind(&WebMediaPlayerImpl::OnOverlayRoutingToken, weak_this_));
+        base::BindOnce(&WebMediaPlayerImpl::OnOverlayRoutingToken, weak_this_));
     request_routing_token_cb_.Run(token_available_cb_.callback());
   }
 

media/blink/webmediaplayer_impl.h

@@ -835,7 +835,7 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   std::unique_ptr<RendererFactorySelector> renderer_factory_selector_;
 
   // For canceling AndroidOverlay routing token requests.
-  base::CancelableCallback<void(const base::UnguessableToken&)>
+  base::CancelableOnceCallback<void(const base::UnguessableToken&)>
       token_available_cb_;
 
   // If overlay info is requested before we have it, then the request is saved