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

chrome/renderer/searchbox/searchbox_extension.cc

 // Copyright 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/renderer/searchbox/searchbox_extension.h"
 
 #include "base/command_line.h"
 #include "base/i18n/rtl.h"
 #include "base/json/string_escape.h"
 #include "base/metrics/field_trial.h"
@@ skipping 99 matching lines @@
 v8::Local<v8::String> GenerateThumbnailURL(
     v8::Isolate* isolate,
     int render_view_id,
     InstantRestrictedID most_visited_item_id) {
   return UTF8ToV8String(
       isolate,
       base::StringPrintf(
           "chrome-search://thumb/%d/%d", render_view_id, most_visited_item_id));
 }
 
-v8::Local<v8::String> GenerateThumb2URL(v8::Isolate* isolate, std::string url) {
+v8::Local<v8::String> GenerateThumb2URL(v8::Isolate* isolate,
+                                        const std::string& url) {
   return UTF8ToV8String(
       isolate, base::StringPrintf("chrome-search://thumb2/%s", url.c_str()));
 }
 
 // Populates a Javascript MostVisitedItem object from |mv_item|.
 // NOTE: Includes "url", "title" and "domain" which are private data, so should
 // not be returned to the Instant page. These should be erased before returning
 // the object. See GetMostVisitedItemsWrapper() in searchbox_api.js.
 v8::Local<v8::Object> GenerateMostVisitedItem(
     v8::Isolate* isolate,
@@ skipping 1177 matching lines @@
   if (!render_view) return;
 
   bool display_instant_results =
       SearchBox::Get(render_view)->display_instant_results();
   DVLOG(1) << render_view << " GetDisplayInstantResults" <<
       display_instant_results;
   args.GetReturnValue().Set(display_instant_results);
 }
 
 }  // namespace extensions_v8