[remoting][mobile] Change signaling timeout message to host-is-offline

In Tachyon context signaling timeout basically means the host is not
reachable, or simply the host is offline. Neither does service
unavailable nor P2P failure convey that message well. This CL changes
the error message on mobile clients for signaling timeout to
host-is-offline.

Change-Id: I72ee4fde896dd36bdda1b7a7c52c5ec582ac94d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1841741
Auto-Submit: Yuwei Huang <yuweih@chromium.org>
Commit-Queue: Jamie Walch <jamiewalch@chromium.org>
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703029}

remoting/android/java/src/org/chromium/chromoting/jni/ConnectionListener.java

@@ -73,7 +73,7 @@ public interface ConnectionListener {
             case Error.SIGNALING_ERROR:
                 return R.string.error_p2p_failure;
             case Error.SIGNALING_TIMEOUT:
-                return R.string.error_p2p_failure;
+                return R.string.error_host_is_offline;
             case Error.HOST_OVERLOAD:
                 return R.string.error_host_overload;
             case Error.MAX_SESSION_LENGTH:

remoting/ios/app/client_connection_view_controller.mm

@@ -552,7 +552,7 @@ using EntryPoint = remoting::ChromotingEvent::SessionEntryPoint;
       message = l10n_util::GetNSString(IDS_ERROR_P2P_FAILURE);
       break;
     case SessionErrorSignalingTimeout:
-      message = l10n_util::GetNSString(IDS_ERROR_SERVICE_UNAVAILABLE);
+      message = l10n_util::GetNSString(IDS_ERROR_HOST_IS_OFFLINE);
       break;
     case SessionErrorHostOverload:
       message = l10n_util::GetNSString(IDS_ERROR_HOST_OVERLOAD);