Update gwtjsonrpc to 1.4

Change-Id: If2b9414c9efd73c29333bb1e8cec2230cd8b5f7f
diff --git a/lib/BUCK b/lib/BUCK
index ac49307..9902422 100644
--- a/lib/BUCK
+++ b/lib/BUCK
@@ -34,9 +34,9 @@
 
 maven_jar(
   name = 'gwtjsonrpc',
-  id = 'gwtjsonrpc:gwtjsonrpc:1.3',
-  bin_sha1 = '1717ba11ab0c5160798c80085220a63f864691d3',
-  src_sha1 = '9e01c5d7bd54f8e70066450b372a43c16404789e',
+  id = 'gwtjsonrpc:gwtjsonrpc:1.4',
+  bin_sha1 = '7500577cbf3afc3395ce15a2f5bccc4b02b0d497',
+  src_sha1 = '589e8eeb4663ee7ba330275ccfac2d6b2c6f28db',
   license = 'Apache2.0',
   repository = GERRIT,
 )