Mark URLs with empty schemes as invalid.

url/url_canon_etc.cc

Index: url/url_canon_etc.cc
diff --git a/url/url_canon_etc.cc b/url/url_canon_etc.cc
index e9da94cca39061c2daf0b7d076993657613ecc6b..9dd40da1624834ea9a3c38b2a5b9c9f6cac31b6b 100644
--- a/url/url_canon_etc.cc
+++ b/url/url_canon_etc.cc
@@ -89,7 +89,7 @@ bool DoScheme(const CHAR* spec,
     // Scheme is unspecified or empty, convert to empty by appending a colon.
     *out_scheme = Component(output->length(), 0);
     output->push_back(':');
-    return true;
+    return false;
   }
 
   // The output scheme starts from the current position.