Cleanup: Pass std::string as const reference if possible

net/base/ip_pattern_unittest.cc

 // Copyright 2014 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 "net/base/ip_pattern.h"
 
 #include "net/base/ip_address_number.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace net {
 
 namespace {
 
 bool IsValidPattern(const std::string& pattern_text) {
   IPPattern pattern;
   return pattern.ParsePattern(pattern_text);
 }
 
-bool CheckForMatch(const IPPattern& pattern, std::string address_text) {
+bool CheckForMatch(const IPPattern& pattern, const std::string& address_text) {
   IPAddressNumber address;
   EXPECT_TRUE(ParseIPLiteralToNumber(address_text, &address));
   return pattern.Match(address);
 }
 
 TEST(IPPatternTest, EmptyPattern) {
   IPPattern pattern;
   IPAddressNumber ipv4_address1;
   EXPECT_TRUE(ParseIPLiteralToNumber("1.2.3.4", &ipv4_address1));
   IPAddressNumber ipv6_address1;
@@ skipping 122 matching lines @@
   EXPECT_FALSE(IsValidPattern("1.2.3.4.5"));  // Too long
   EXPECT_FALSE(IsValidPattern("1.2.3"));  // Too short
   EXPECT_FALSE(IsValidPattern("1.2.3.A"));  // Non-decimal.
   EXPECT_FALSE(IsValidPattern("1.A.3.4"));  // Non-decimal
   EXPECT_FALSE(IsValidPattern("1.256.3.4"));  // Out of range
 }
 
 }  // namespace
 
 }  // namespace net