doc: Mention when protocol module is safe to use.

diff --git a/docs/api/browser/protocol.md b/docs/api/browser/protocol.md
index ec6c1f2..7e566ba 100644 (file)
--- a/docs/api/browser/protocol.md
+++ b/docs/api/browser/protocol.md
@@ -14,6 +14,9 @@ protocol.registerProtocol('atom', function(request) {
 });
 ```
 
+**Note:** This module can only be used after the `will-finish-launching` event
+was emitted.
+
 ## protocol.registerProtocol(scheme, handler)
 
 * `scheme` String