Move referrer stripping into GURL::GetAsReferrer().

url/gurl.cc

Index: url/gurl.cc
diff --git a/url/gurl.cc b/url/gurl.cc
index 8eb2d6132db5ef0c7636ab5a73dc87b843f7d5ae..77b8def28c4604d546202420bb78bc9d21eba4b4 100644
--- a/url/gurl.cc
+++ b/url/gurl.cc
@@ -320,6 +320,18 @@ GURL GURL::GetOrigin() const {
   return ReplaceComponents(replacements);
 }
 
+GURL GURL::GetAsReferrer() const {
+  if (!is_valid_ ||
+      (!has_ref() && !has_username() && !has_password()))
+    return GURL(*this);
+
+  url_canon::Replacements<char> replacements;
+  replacements.ClearRef();
+  replacements.ClearUsername();
+  replacements.ClearPassword();
+  return ReplaceComponents(replacements);
+}
+
 GURL GURL::GetWithEmptyPath() const {
   // This doesn't make sense for invalid or nonstandard URLs, so return
   // the empty URL.