Add audible support to the copresence API.

components/copresence/public/copresence_client.h

Index: components/copresence/public/copresence_client.h
diff --git a/components/copresence/public/copresence_client.h b/components/copresence/public/copresence_client.h
index 867276a44cb365bd7ad3ef70d98595a559c177e8..d8bb61b5e6f9c0a8b0c0429c38fa7ff72f7c7b03 100644
--- a/components/copresence/public/copresence_client.h
+++ b/components/copresence/public/copresence_client.h
@@ -11,6 +11,7 @@
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 #include "components/copresence/proto/rpcs.pb.h"
 #include "components/copresence/public/copresence_client_delegate.h"
 
@@ -38,7 +39,7 @@ struct PendingRequest {
 // functionality. This class handles all the initialization and delegation of
 // copresence tasks. Any user of copresence only needs to interact with this
 // client.
-class CopresenceClient {
+class CopresenceClient : public base::SupportsWeakPtr<CopresenceClient> {
  public:
   // The delegate must outlive us.
   explicit CopresenceClient(CopresenceClientDelegate* delegate);