Ignore UTF-8's BOM when parsing userscript's metadata.

chrome/browser/extensions/user_script_master.cc

Index: chrome/browser/extensions/user_script_master.cc
diff --git a/chrome/browser/extensions/user_script_master.cc b/chrome/browser/extensions/user_script_master.cc
index c9228ffc462880d9e97b953ab8eb2182f37410fa..a485a41911d3d13cd984faf895867ee7f1a91bcd 100644
--- a/chrome/browser/extensions/user_script_master.cc
+++ b/chrome/browser/extensions/user_script_master.cc
@@ -46,7 +46,12 @@ bool UserScriptMaster::ScriptReloader::ParseMetadataHeader(
   // http://wiki.greasespot.net/Metadata_block
   base::StringPiece line;
   size_t line_start = 0;
-  size_t line_end = 0;
+
+  // Skip UTF-8's BOM.
+  if (script_text.starts_with(kUtf8ByteOrderMark))
+    line_start += strlen(kUtf8ByteOrderMark);
+
+  size_t line_end = line_start;
   bool in_metadata = false;
 
   static const base::StringPiece kUserScriptBegin("// ==UserScript==");