Coverity: Fix several pass-by-values.

chrome/common/extensions/url_pattern.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/common/extensions/url_pattern.h"
 
 #include "base/string_number_conversions.h"
 #include "base/string_piece.h"
 #include "base/string_split.h"
 #include "base/string_util.h"
@@ skipping 58 matching lines @@
 
 bool IsStandardScheme(const std::string& scheme) {
   // "*" gets the same treatment as a standard scheme.
   if (scheme == "*")
     return true;
 
   return url_util::IsStandard(scheme.c_str(),
       url_parse::Component(0, static_cast<int>(scheme.length())));
 }
 
-bool IsValidPortForScheme(const std::string scheme, const std::string& port) {
+bool IsValidPortForScheme(const std::string& scheme, const std::string& port) {
   if (port == "*")
     return true;
 
   // Only accept non-wildcard ports if the scheme uses ports.
   if (url_canon::DefaultPortForScheme(scheme.c_str(), scheme.length()) ==
       url_parse::PORT_UNSPECIFIED) {
     return false;
   }
 
   int parsed_port = url_parse::PORT_UNSPECIFIED;
@@ skipping 424 matching lines @@
   }
 
   return result;
 }
 
 // static
 const char* URLPattern::GetParseResultString(
     URLPattern::ParseResult parse_result) {
   return kParseResultMessages[parse_result];
 }