Use ChannelMojo for remote security key channels.

remoting/host/security_key/security_key_ipc_constants.h

Index: remoting/host/security_key/security_key_ipc_constants.h
diff --git a/remoting/host/security_key/security_key_ipc_constants.h b/remoting/host/security_key/security_key_ipc_constants.h
index 236e6d9749bf4c6943535ec54efa7782cd33831b..ce183dd83298043843a399b7f2bebdbc78e7d2c6 100644
--- a/remoting/host/security_key/security_key_ipc_constants.h
+++ b/remoting/host/security_key/security_key_ipc_constants.h
@@ -7,6 +7,8 @@
 
 #include <string>
 
+#include "mojo/edk/embedder/named_platform_handle.h"
+
 namespace remoting {
 
 // Used to indicate an error during a security key forwarding session.
@@ -14,10 +16,11 @@ extern const char kSecurityKeyConnectionError[];
 
 // Returns the name of the well-known IPC server channel used to initiate a
 // security key forwarding session.
-const std::string& GetSecurityKeyIpcChannelName();
+const mojo::edk::NamedPlatformHandle& GetSecurityKeyIpcChannel();
 
 // Sets the name of the well-known IPC server channel for testing purposes.
-void SetSecurityKeyIpcChannelNameForTest(const std::string& channel_name);
+void SetSecurityKeyIpcChannelForTest(
+    const mojo::edk::NamedPlatformHandle& channel_handle);
 
 // Returns a path appropriate for placing a channel name.  Without this path
 // prefix, we may not have permission on linux to bind(2) a socket to a name in