Relax threading restrictions

VolumeControlAndroid should be allowed to perform these operations.
See internal bug #15 for details.

Bug: internal b/174680080
Test: on device
Change-Id: I654c8c33c5991894cd44ba2bedfa08f2f1eb7288
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2572131
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Commit-Queue: Andrei Pascovici <apascovici@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833734}

chromecast/media/cma/backend/android/volume_control_android.cc

@@ -133,7 +133,8 @@ void VolumeControlAndroid::OnVolumeChange(
   thread_.task_runner()->PostTask(
       FROM_HERE,
       base::BindOnce(&VolumeControlAndroid::ReportVolumeChangeOnThread,
-                     base::Unretained(this), (AudioContentType)type, level));
+                     base::Unretained(this),
+                     static_cast<AudioContentType>(type), level));
 }
 
 void VolumeControlAndroid::OnMuteChange(
@@ -142,9 +143,9 @@ void VolumeControlAndroid::OnMuteChange(
     jint type,
     jboolean muted) {
   thread_.task_runner()->PostTask(
-      FROM_HERE,
-      base::BindOnce(&VolumeControlAndroid::ReportMuteChangeOnThread,
-                     base::Unretained(this), (AudioContentType)type, muted));
+      FROM_HERE, base::BindOnce(&VolumeControlAndroid::ReportMuteChangeOnThread,
+                                base::Unretained(this),
+                                static_cast<AudioContentType>(type), muted));
 }
 
 #if BUILDFLAG(ENABLE_VOLUME_TABLES_ACCESS)
@@ -335,7 +336,7 @@ float VolumeControlAndroid::DbFSToVolumeCached(AudioContentType type,
 
 // static
 void VolumeControl::Initialize(const std::vector<std::string>& argv) {
-  // Nothing to do.
+  GetVolumeControl();
 }
 
 // static