[Chromecast] Use mojo::Receiver in VideoGeometrySetterService.

Change |video_geometry_setter_receivers_| from mojo::ReceiverSet
to mojo::Receiver because a single receiver is more appropriate.

Bug: 925450
Test: Cast youtube with and without VizDisplayCompositor enabled.
Change-Id: I7bd60820297a54e3a84bf268a015cb4625da7199
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1927223Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Commit-Queue: Guohui Deng <guohuideng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718309}

chromecast/media/service/video_geometry_setter_service.cc

@@ -39,7 +39,11 @@ void VideoGeometrySetterService::GetVideoGeometryChangeSubscriber(
 void VideoGeometrySetterService::GetVideoGeometrySetter(
     mojo::PendingReceiver<mojom::VideoGeometrySetter> pending_receiver) {
   MAKE_SURE_ON_SEQUENCE(GetVideoGeometrySetter, std::move(pending_receiver));
-  video_geometry_setter_receivers_.Add(this, std::move(pending_receiver));
+  if (video_geometry_setter_receiver_.is_bound()) {
+    LOG(ERROR) << __func__ << " VideoGeometrySetter dropped";
+    video_geometry_setter_receiver_.reset();
+  }
+  video_geometry_setter_receiver_.Bind(std::move(pending_receiver));
 }
 
 void VideoGeometrySetterService::SubscribeToVideoGeometryChange(

chromecast/media/service/video_geometry_setter_service.h

@@ -17,6 +17,7 @@
 #include "chromecast/media/service/mojom/video_geometry_setter.mojom.h"
 #include "mojo/public/cpp/bindings/pending_receiver.h"
 #include "mojo/public/cpp/bindings/pending_remote.h"
+#include "mojo/public/cpp/bindings/receiver.h"
 #include "mojo/public/cpp/bindings/receiver_set.h"
 
 namespace base {
@@ -64,9 +65,8 @@ class VideoGeometrySetterService : public mojom::VideoGeometryChangeSubscriber,
 
   mojo::ReceiverSet<mojom::VideoGeometryChangeSubscriber>
       video_geometry_change_subscriber_receivers_;
-  // TODO(guohuideng): change mojo::ReceiverSet to mojo::Receiver.
-  mojo::ReceiverSet<mojom::VideoGeometrySetter>
-      video_geometry_setter_receivers_;
+  mojo::Receiver<mojom::VideoGeometrySetter> video_geometry_setter_receiver_{
+      this};
 
   base::WeakPtrFactory<VideoGeometrySetterService> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(VideoGeometrySetterService);