Remove support for the "gcm_user_visible_only" manifest key.

content/renderer/manifest/manifest_parser.h

Index: content/renderer/manifest/manifest_parser.h
diff --git a/content/renderer/manifest/manifest_parser.h b/content/renderer/manifest/manifest_parser.h
index 4beb55ed860cdd5da7a57fdc88096f2415391bac..f8817314fd09c76ea44b8dd9b16bb89b0f73d6c8 100644
--- a/content/renderer/manifest/manifest_parser.h
+++ b/content/renderer/manifest/manifest_parser.h
@@ -161,11 +161,6 @@ class CONTENT_EXPORT ManifestParser {
   base::NullableString16 ParseGCMSenderID(
       const base::DictionaryValue& dictionary);
 
-  // Parses the 'gcm_user_visible_only' field of the manifest.
-  // This is a proprietary extension of the Web Manifest specification.
-  // Returns true iff the string could be parsed as the boolean true.
-  bool ParseGCMUserVisibleOnly(const base::DictionaryValue& dictionary);
-
   const base::StringPiece& data_;
   GURL manifest_url_;
   GURL document_url_;