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

pdf/pdfium/pdfium_page.cc

 // Copyright (c) 2010 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 "pdf/pdfium/pdfium_page.h"
 
 #include <math.h>
 
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 222 matching lines @@
     if (before_text.size() > 0)
       text_nodes->Append(CreateTextNode(before_text));
   } else {
     text_nodes->Append(CreateTextNode(text_utf8));
   }
 
   node->Set(kTextBoxNodes, text_nodes);  // Takes ownership of |text_nodes|.
   return node;
 }
 
-base::Value* PDFiumPage::CreateTextNode(std::string text) {
+base::Value* PDFiumPage::CreateTextNode(const std::string& text) {
   base::DictionaryValue* node = new base::DictionaryValue();
   node->SetString(kTextNodeType, kTextNodeTypeText);
   node->SetString(kTextNodeText, text);
   return node;
 }
 
-base::Value* PDFiumPage::CreateURLNode(std::string text, std::string url) {
+base::Value* PDFiumPage::CreateURLNode(const std::string& text,
+                                       const std::string& url) {
   base::DictionaryValue* node = new base::DictionaryValue();
   node->SetString(kTextNodeType, kTextNodeTypeURL);
   node->SetString(kTextNodeText, text);
   node->SetString(kTextNodeURL, url);
   return node;
 }
 
 PDFiumPage::Area PDFiumPage::GetCharIndex(const pp::Point& point,
                                           int rotation,
                                           int* char_index,
@@ skipping 265 matching lines @@
   page_->loading_count_--;
 }
 
 PDFiumPage::Link::Link() {
 }
 
 PDFiumPage::Link::~Link() {
 }
 
 }  // namespace chrome_pdf