Redesign the copresence audio handlers.

components/copresence/handlers/audio/audio_directive_list.h

Index: components/copresence/handlers/audio/audio_directive_list.h
diff --git a/components/copresence/handlers/audio/audio_directive_list.h b/components/copresence/handlers/audio/audio_directive_list.h
index 9edd89f49b07c7ced741e44c62d9415989c555ee..12c64ceb617553b45fdef829e8734808d0b45a60 100644
--- a/components/copresence/handlers/audio/audio_directive_list.h
+++ b/components/copresence/handlers/audio/audio_directive_list.h
@@ -19,7 +19,7 @@ class AudioBusRefCounted;
 
 namespace copresence {
 
-struct AudioDirective {
+struct AudioDirective final {
   // Default ctor, required by the priority queue.
   AudioDirective();
   AudioDirective(const std::string& op_id, base::Time end_time);
@@ -37,7 +37,7 @@ struct AudioDirective {
 class AudioDirectiveList {
  public:
   AudioDirectiveList();
-  virtual ~AudioDirectiveList();
+  ~AudioDirectiveList();
 
   void AddDirective(const std::string& op_id, base::TimeDelta ttl);
   void RemoveDirective(const std::string& op_id);