[jumbo] add some missing include guards in //remoting

Change-Id: I4e087b8b1da557d6c85dd8c87b678b1fa62bba5f
Reviewed-on: https://chromium-review.googlesource.com/883624
Reviewed-by: Joe Downing <[email protected]>
Commit-Queue: Mostyn Bramley-Moore <[email protected]>
Cr-Commit-Position: refs/heads/master@{#531742}
diff --git a/remoting/host/host_secret.h b/remoting/host/host_secret.h
index 63fe590..bb600c9 100644
--- a/remoting/host/host_secret.h
+++ b/remoting/host/host_secret.h
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#ifndef REMOTING_HOST_HOST_SECRET_H_
+#define REMOTING_HOST_HOST_SECRET_H_
+
 #include <string>
 
 namespace remoting {
@@ -10,3 +13,5 @@
 std::string GenerateSupportHostSecret();
 
 }  // namespace remoting
+
+#endif  // REMOTING_HOST_HOST_SECRET_H_