Motown: Don't build out pipelines for streams that don't get rendered.

services/media/factory_service/media_player_impl.cc

 // Copyright 2016 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 "base/logging.h"
 #include "mojo/public/cpp/application/connect.h"
 #include "mojo/services/media/common/cpp/timeline.h"
 #include "services/media/factory_service/media_player_impl.h"
 #include "services/media/framework/parts/reader.h"
 #include "services/media/framework/util/callback_joiner.h"
@@ skipping 47 matching lines @@
 
   demux_->Describe([this](mojo::Array<MediaTypePtr> stream_types) {
     // Populate streams_ and enable the streams we want.
     std::shared_ptr<CallbackJoiner> callback_joiner = CallbackJoiner::Create();
 
     for (MediaTypePtr& stream_type : stream_types) {
       streams_.push_back(std::unique_ptr<Stream>(new Stream()));
       Stream& stream = *streams_.back();
       switch (stream_type->medium) {
         case MediaTypeMedium::AUDIO:
-          stream.renderer_ = audio_renderer_.Pass();
-          PrepareStream(&stream, streams_.size() - 1, stream_type,
-                        callback_joiner->NewCallback());
+          if (audio_renderer_) {
+            stream.renderer_ = audio_renderer_.Pass();
+            PrepareStream(&stream, streams_.size() - 1, stream_type,
+                          callback_joiner->NewCallback());
+          }
           break;
         case MediaTypeMedium::VIDEO:
-          stream.renderer_ = video_renderer_.Pass();
-          PrepareStream(&stream, streams_.size() - 1, stream_type,
-                        callback_joiner->NewCallback());
+          if (video_renderer_) {
+            stream.renderer_ = video_renderer_.Pass();
+            PrepareStream(&stream, streams_.size() - 1, stream_type,
+                          callback_joiner->NewCallback());
+          }
           break;
         // TODO(dalesat): Enable other stream types.
         default:
           break;
       }
     }
 
     callback_joiner->WhenJoined([this]() {
       // The enabled streams are prepared.
       factory_.reset();
@@ skipping 289 matching lines @@
         HandleTimelineControlSiteStatusUpdates(version, status.Pass());
       });
 }
 
 MediaPlayerImpl::Stream::Stream() {}
 
 MediaPlayerImpl::Stream::~Stream() {}
 
 }  // namespace media
 }  // namespace mojo