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

chrome/browser/ui/ash/launcher/chrome_launcher_controller.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 "chrome/browser/ui/ash/launcher/chrome_launcher_controller.h"
 
 #include <vector>
 
 #include "ash/ash_switches.h"
 #include "ash/desktop_background/desktop_background_controller.h"
@@ skipping 1264 matching lines @@
   // Make sure that there is a controller associated with the id and that the
   // extension itself is a valid application and not a panel.
   LauncherItemController* controller = GetLauncherItemController(item.id);
   if (!controller || !GetShelfIDForAppID(controller->app_id()))
     return ChromeLauncherAppMenuItems().Pass();
 
   return controller->GetApplicationList(event_flags);
 }
 
 std::vector<content::WebContents*>
-ChromeLauncherController::GetV1ApplicationsFromAppId(std::string app_id) {
+ChromeLauncherController::GetV1ApplicationsFromAppId(
+    const std::string& app_id) {
   ash::ShelfID id = GetShelfIDForAppID(app_id);
 
   // If there is no such an item pinned to the launcher, no menu gets created.
   if (id) {
     LauncherItemController* controller = GetLauncherItemController(id);
     DCHECK(controller);
     if (controller->type() == LauncherItemController::TYPE_SHORTCUT)
       return GetV1ApplicationsFromController(controller);
   }
   return std::vector<content::WebContents*>();
@@ skipping 807 matching lines @@
 void ChromeLauncherController::ReleaseProfile() {
   if (app_sync_ui_state_)
     app_sync_ui_state_->RemoveObserver(this);
 
   extensions::ExtensionRegistry::Get(profile_)->RemoveObserver(this);
 
   PrefServiceSyncableFromProfile(profile_)->RemoveObserver(this);
 
   pref_change_registrar_.RemoveAll();
 }