Make sync_type non const to allow updates to it.

Bug: internal b/104824337
Change-Id: I866cfa171eb11bdd401f3892233b970310fc45ac
Reviewed-on: https://chromium-review.googlesource.com/1186116Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: Mohit Hotwani <hmohit@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585382}

chromecast/public/media/media_pipeline_device_params.h

@@ -72,7 +72,7 @@ struct MediaPipelineDeviceParams {
   MediaPipelineDeviceParams(const MediaPipelineDeviceParams& other);
   MediaPipelineDeviceParams(MediaPipelineDeviceParams&& other);
 
-  const MediaSyncType sync_type;
+  MediaSyncType sync_type;
   const AudioStreamType audio_type;
 
   // task_runner allows backend implementations to post tasks to the media