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

components/policy/core/browser/policy_error_map.cc

 // Copyright 2013 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/policy/core/browser/policy_error_map.h"
 
 #include <utility>
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/strings/grit/components_strings.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/resource/resource_bundle.h"
 
 namespace policy {
 
 class PolicyErrorMap::PendingError {
  public:
@@ skipping 162 matching lines @@
 void PolicyErrorMap::AddError(const std::string& policy,
                               const std::string& error_path,
                               const std::string& message) {
   AddError(base::MakeUnique<SchemaValidatingPendingError>(policy, error_path,
                                                           message));
 }
 
 base::string16 PolicyErrorMap::GetErrors(const std::string& policy) {
   CheckReadyAndConvert();
   std::pair<const_iterator, const_iterator> range = map_.equal_range(policy);
-  std::vector<base::string16> list;
+  std::vector<base::StringPiece16> list;
   for (const_iterator it = range.first; it != range.second; ++it)
     list.push_back(it->second);
   return base::JoinString(list, base::ASCIIToUTF16("\n"));
 }
 
 bool PolicyErrorMap::empty() {
   CheckReadyAndConvert();
   return map_.empty();
 }
 
@@ skipping 32 matching lines @@
 
 void PolicyErrorMap::CheckReadyAndConvert() {
   DCHECK(IsReady());
   for (size_t i = 0; i < pending_.size(); ++i) {
     Convert(pending_[i].get());
   }
   pending_.clear();
 }
 
 }  // namespace policy