IPC: Remove unnecessary conversions of BrokerableAttachment.

ipc/attachment_broker.h

Index: ipc/attachment_broker.h
diff --git a/ipc/attachment_broker.h b/ipc/attachment_broker.h
index 36489d4ee9dc8133e7184aceec9cb31e19152a9f..a0155875c134c400985de64b85cc6647ae8699db 100644
--- a/ipc/attachment_broker.h
+++ b/ipc/attachment_broker.h
@@ -7,6 +7,7 @@
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
+#include "base/memory/ref_counted.h"
 #include "base/process/process_handle.h"
 #include "ipc/brokerable_attachment.h"
 #include "ipc/ipc_export.h"
@@ -65,8 +66,9 @@ class IPC_EXPORT AttachmentBroker : public Listener {
   // IPC::Channel to communicate with the broker process. This may be the same
   // IPC::Channel that is requesting the brokering of an attachment.
   // Returns true on success and false otherwise.
-  virtual bool SendAttachmentToProcess(BrokerableAttachment* attachment,
-                                       base::ProcessId destination_process) = 0;
+  virtual bool SendAttachmentToProcess(
+      const scoped_refptr<BrokerableAttachment>& attachment,
+      base::ProcessId destination_process) = 0;
 
   // Returns whether the attachment was available. If the attachment was
   // available, populates the output parameter |attachment|.