[chromecast] Track MediaPipelineBackend used by CastRenderer.

chromecast/media/base/media_resource_tracker.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 "chromecast/media/base/media_resource_tracker.h"
 
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
 #include "chromecast/base/bind_to_task_runner.h"
 #include "chromecast/public/cast_media_shlib.h"
 
 namespace chromecast {
 namespace media {
 
+MediaResourceTracker::ScopedUsage::ScopedUsage(MediaResourceTracker* tracker)
+    : tracker_(tracker) {
+  DCHECK(tracker_);
+  DCHECK(tracker_->media_task_runner_->BelongsToCurrentThread());
+  tracker_->IncrementUsageCount();
+}
+
+MediaResourceTracker::ScopedUsage::~ScopedUsage() {
+  DCHECK(tracker_->media_task_runner_->BelongsToCurrentThread());
+  tracker_->DecrementUsageCount();
+}
+
 MediaResourceTracker::MediaResourceTracker(
     const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner,
     const scoped_refptr<base::SingleThreadTaskRunner>& media_task_runner)
     : media_use_count_(0),
       media_lib_initialized_(false),
       delete_on_finalize_(false),
       ui_task_runner_(ui_task_runner),
       media_task_runner_(media_task_runner) {
   DCHECK(ui_task_runner);
   DCHECK(media_task_runner);
@@ skipping 111 matching lines @@
   base::CommandLine* cmd_line = base::CommandLine::ForCurrentProcess();
   media::CastMediaShlib::Initialize(cmd_line->argv());
 }
 
 void MediaResourceTracker::DoFinalizeMediaLib() {
   CastMediaShlib::Finalize();
 }
 
 }  // namespace media
 }  // namespace chromecast