remoting: Add IPC message to save new OAuth refresh token.

As part of the migration from Talk to FTL, we need to fetch new OAuth
tokens with additonal scopes. This fetching will happen in the network
process, which has no filesystem access. This new message will allow the
network process to inform the daemon process of the new token, so the
daemon process can update the on-disk config file accordingly.

Bug: 954427
Change-Id: I59d0498abe9d31c4789a95ff1371d700728eabca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1625925Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Joe Downing <joedow@chromium.org>
Commit-Queue: Joe Downing <joedow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662485}

remoting/host/chromoting_messages.h

@@ -124,6 +124,11 @@ IPC_MESSAGE_CONTROL(ChromotingNetworkDaemonMsg_HostStarted,
 
 IPC_MESSAGE_CONTROL(ChromotingNetworkDaemonMsg_HostShutdown)
 
+// Instructs the daemon process to update the config file, replacing the current
+// OAuth refresh token with the one provided.
+IPC_MESSAGE_CONTROL(ChromotingNetworkDaemonMsg_UpdateConfigRefreshToken,
+                    std::string /* token */)
+
 //-----------------------------------------------------------------------------
 // Chromoting messages sent from the desktop to the daemon process.