Allow tail to not be trimmed.

url/url_canon_relative.cc

Index: url/url_canon_relative.cc
diff --git a/url/url_canon_relative.cc b/url/url_canon_relative.cc
index a61eaa0651de89ff01024f58431d7472778d0ca8..0abef40ff860b285b6a36d73b988e02db3e709b8 100644
--- a/url/url_canon_relative.cc
+++ b/url/url_canon_relative.cc
@@ -105,12 +105,11 @@ bool DoIsRelativeURL(const char* base,
   const url_parse::Component& scheme = url_parsed.scheme;
   const bool scheme_is_empty = !scheme.is_nonempty();
   if (scheme_is_empty) {
-    // No scheme. See if is a bare fragment.
-    if (url_parsed.ref.is_valid() &&
+    // |url| has no scheme. Check the other extreme: is it a bare fragment.
+    bool url_is_ref_only = url_parsed.ref.is_valid() &&
         url_parsed.CountCharactersBefore(url_parse::Parsed::REF, true) ==
-        url_parsed.CountCharactersBefore(url_parse::Parsed::SCHEME, false)) {
-      // |url| is a bare fragement. This can be resolved against any base.
-    } else if (!is_base_hierarchical) {
+        url_parsed.CountCharactersBefore(url_parse::Parsed::SCHEME, false);
+    if (!url_is_ref_only && !is_base_hierarchical) {
       // Don't allow relative URLs if the base scheme doesn't support it.
       return false;
     }