Load CMA backend from shared library

chromecast/public/media/media_pipeline_device_params.h

Index: chromecast/public/media/media_pipeline_device_params.h
diff --git a/chromecast/media/cma/backend/media_pipeline_device_params.h b/chromecast/public/media/media_pipeline_device_params.h
similarity index 64%
rename from chromecast/media/cma/backend/media_pipeline_device_params.h
rename to chromecast/public/media/media_pipeline_device_params.h
index d13e4e3a188b948829e4886b96f1e0d7c2baba6c..62a6be7955634731d7de0fc43a32945308cbe758 100644
--- a/chromecast/media/cma/backend/media_pipeline_device_params.h
+++ b/chromecast/public/media/media_pipeline_device_params.h
@@ -2,16 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_PIPELINE_DEVICE_PARAMS_H_
-#define CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_PIPELINE_DEVICE_PARAMS_H_
+#ifndef CHROMECAST_PUBLIC_MEDIA_MEDIA_PIPELINE_DEVICE_PARAMS_H_
+#define CHROMECAST_PUBLIC_MEDIA_MEDIA_PIPELINE_DEVICE_PARAMS_H_
 
-#include "base/macros.h"
+#include "task_runner.h"
 
 namespace chromecast {
 namespace media {
 
-class MediaPipelineDeviceParams {
- public:
+struct MediaPipelineDeviceParams {
   enum MediaSyncType {
     // Default operation, synchronize playback using PTS with higher latency.
     kModeSyncPts = 0,
@@ -27,10 +26,16 @@ class MediaPipelineDeviceParams {
     kModeIgnorePtsAndVSync = 2,
   };
 
-  MediaPipelineDeviceParams();
-  ~MediaPipelineDeviceParams();
+  MediaPipelineDeviceParams(TaskRunner* task_runner_in)
+      : sync_type(kModeSyncPts), task_runner(task_runner_in) {}
 
   MediaSyncType sync_type;
+
+  // task_runner allows backend implementations to post tasks to the media
+  // thread.  Since all calls from cast_shell into the backend are made on
+  // the media thread, this may simplify thread management and safety for
+  // some backends.
+  TaskRunner* const task_runner;
 };
 
 }  // namespace media