[Extensions] Code cleanup - const &s

chrome/common/extensions/chrome_manifest_url_handlers.cc

 // Copyright (c) 2012 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/common/extensions/chrome_manifest_url_handlers.h"
 
 #include <memory>
 
 #include "base/files/file_util.h"
 #include "base/lazy_instance.h"
@@ skipping 85 matching lines @@
   const base::DictionaryValue* overrides = NULL;
   if (!extension->manifest()->GetDictionary(keys::kChromeURLOverrides,
                                             &overrides)) {
     *error = base::ASCIIToUTF16(errors::kInvalidChromeURLOverrides);
     return false;
   }
   std::unique_ptr<URLOverrides> url_overrides(new URLOverrides);
   // Validate that the overrides are all strings
   for (base::DictionaryValue::Iterator iter(*overrides); !iter.IsAtEnd();
        iter.Advance()) {
-    std::string page = iter.key();
+    const std::string& page = iter.key();
     std::string val;
     // Restrict override pages to a list of supported URLs.
     bool is_allowed_host = page == chrome::kChromeUINewTabHost ||
                            page == chrome::kChromeUIBookmarksHost ||
                            page == chrome::kChromeUIHistoryHost;
 #if defined(OS_CHROMEOS)
     is_allowed_host = is_allowed_host ||
                       page == chrome::kChromeUIActivationMessageHost ||
                       page == keyboard::kKeyboardHost;
 #endif
@@ skipping 51 matching lines @@
     }
   }
   return true;
 }
 
 const std::vector<std::string> URLOverridesHandler::Keys() const {
   return SingleKey(keys::kChromeURLOverrides);
 }
 
 }  // namespace extensions