Change uses of base::JoinString to pass StringPieces where possible.

chrome/browser/net/safe_search_util.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 "chrome/browser/net/safe_search_util.h"
 
 #include <string>
 #include <utility>
 #include <vector>
 
@@ skipping 15 matching lines @@
 int g_force_google_safe_search_count_for_test = 0;
 int g_force_youtube_restrict_count_for_test = 0;
 
 const char kYouTubeRestrictHeaderName[] = "YouTube-Restrict";
 const char kYouTubeRestrictHeaderValueModerate[] = "Moderate";
 const char kYouTubeRestrictHeaderValueStrict[] = "Strict";
 
 // Returns whether a URL parameter, |first_parameter| (e.g. foo=bar), has the
 // same key as the the |second_parameter| (e.g. foo=baz). Both parameters
 // must be in key=value form.
-bool HasSameParameterKey(const std::string& first_parameter,
-                         const std::string& second_parameter) {
+bool HasSameParameterKey(base::StringPiece first_parameter,
+                         base::StringPiece second_parameter) {
   DCHECK(second_parameter.find("=") != std::string::npos);
   // Prefix for "foo=bar" is "foo=".
-  std::string parameter_prefix = second_parameter.substr(
-      0, second_parameter.find("=") + 1);
+  base::StringPiece parameter_prefix =
+      second_parameter.substr(0, second_parameter.find("=") + 1);
   return base::StartsWith(first_parameter, parameter_prefix,
                           base::CompareCase::INSENSITIVE_ASCII);
 }
 
 // Examines the query string containing parameters and adds the necessary ones
 // so that SafeSearch is active. |query| is the string to examine and the
 // return value is the |query| string modified such that SafeSearch is active.
 std::string AddSafeSearchParameters(const std::string& query) {
-  std::vector<std::string> new_parameters;
+  std::vector<base::StringPiece> new_parameters;
   std::string safe_parameter = chrome::kSafeSearchSafeParameter;
   std::string ssui_parameter = chrome::kSafeSearchSsuiParameter;
 
-  for (const std::string& param : base::SplitString(
-           query, "&", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL)) {
+  for (auto param : base::SplitStringPiece(query, "&", base::TRIM_WHITESPACE,

[Nico, 2017/03/15 13:52:11]

const auto&

(imho, s/auto/base::StringPiece/ is even nicer)

[Matt Giuca, 2017/03/17 00:16:27]

See discussion on
https://codereview.chromium.org/2695883003/diff/270001/base/feature_list.cc#n...
--- I think the StringPiece documentation is asking to be used by value, not by
const reference.

(If we want to change it, I'll have to do it globally throughout this CL because
I used this pattern a lot.)

I don't feel strongly about auto vs StringPiece (and it seems the style guide
doesn't either) so I'll revert it.

[Matt Giuca, 2017/03/27 03:24:58]

Done.

+                                           base::SPLIT_WANT_ALL)) {
     if (!HasSameParameterKey(param, safe_parameter) &&
         !HasSameParameterKey(param, ssui_parameter)) {
       new_parameters.push_back(param);
     }
   }
 
   new_parameters.push_back(safe_parameter);
   new_parameters.push_back(ssui_parameter);
   return base::JoinString(new_parameters, "&");
 }
@@ skipping 61 matching lines @@
 
 void ClearForceGoogleSafeSearchCountForTesting() {
   g_force_google_safe_search_count_for_test = 0;
 }
 
 void ClearForceYouTubeRestrictCountForTesting() {
   g_force_youtube_restrict_count_for_test = 0;
 }
 
 }  // namespace safe_search_util