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

components/flags_ui/flags_state.cc

 // Copyright 2015 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 "components/flags_ui/flags_state.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/callback.h"
 #include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/metrics/field_trial.h"
 #include "base/stl_util.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "build/build_config.h"
 #include "components/flags_ui/feature_entry.h"
 #include "components/flags_ui/flags_storage.h"
 #include "components/flags_ui/flags_ui_switches.h"
 #include "components/variations/variations_associated_data.h"
 #include "ui/base/l10n/l10n_util.h"
 
@@ skipping 356 matching lines @@
     const auto& switch_added_values = entry.second;
 
     // The below is either a std::string or a base::string16 based on platform.
     const auto& existing_value = (*switch_list)[switch_name];
 #if defined(OS_WIN)
     const std::string existing_value_utf8 = base::UTF16ToUTF8(existing_value);
 #else
     const std::string& existing_value_utf8 = existing_value;
 #endif
 
-    std::vector<std::string> features =
+    std::vector<base::StringPiece> features =
         base::FeatureList::SplitFeatureListString(existing_value_utf8);
-    std::vector<std::string> remaining_features;
+    std::vector<base::StringPiece> remaining_features;
     // For any featrue name in |features| that is not in |switch_added_values| -
     // i.e. it wasn't added by about_flags code, add it to |remaining_features|.
-    for (const std::string& feature : features) {
-      if (!base::ContainsKey(switch_added_values, feature))
+    for (const auto& feature : features) {
+      if (!base::ContainsKey(switch_added_values, feature.as_string()))
         remaining_features.push_back(feature);
     }
 
     // Either remove the flag entirely if |remaining_features| is empty, or set
     // the new list.
     if (remaining_features.empty()) {
       switch_list->erase(switch_name);
     } else {
       std::string switch_value = base::JoinString(remaining_features, ",");
 #if defined(OS_WIN)
@@ skipping 267 matching lines @@
   }
 }
 
 void FlagsState::MergeFeatureCommandLineSwitch(
     const std::map<std::string, bool>& feature_switches,
     const char* switch_name,
     bool feature_state,
     base::CommandLine* command_line) {
   std::string original_switch_value =
       command_line->GetSwitchValueASCII(switch_name);
-  std::vector<std::string> features =
+  std::vector<base::StringPiece> features =
       base::FeatureList::SplitFeatureListString(original_switch_value);
   // Only add features that don't already exist in the lists.
   // Note: The base::ContainsValue() call results in O(n^2) performance, but in
   // practice n should be very small.
   for (const auto& entry : feature_switches) {
     if (entry.second == feature_state &&
         !base::ContainsValue(features, entry.first)) {
       features.push_back(entry.first);
       appended_switches_[switch_name].insert(entry.first);
     }
@@ skipping 97 matching lines @@
                               state == FeatureEntry::FeatureState::ENABLED,
                               name_to_switch_map);
           }
         }
         break;
     }
   }
 }
 
 }  // namespace flags_ui