Use a const reference in IntentPickerResponse

chrome/browser/chromeos/arc/arc_navigation_throttle.h

 // Copyright 2016 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_ARC_ARC_NAVIGATION_THROTTLE_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_ARC_NAVIGATION_THROTTLE_H_
 
 #include <memory>
 #include <string>
 #include <utility>
@@ skipping 30 matching lines @@
     PREFERRED_ACTIVITY_FOUND = 4,
     SIZE,
     INVALID = SIZE,
   };
 
   // Restricts the amount of apps displayed to the user without the need of a
   // ScrollView.
   enum { kMaxAppResults = 3 };
 
   struct AppInfo {
-    explicit AppInfo(gfx::Image img, std::string package, std::string activity)
+    AppInfo(gfx::Image img, std::string package, std::string activity)
         : icon(img), package_name(package), activity_name(activity) {}
     gfx::Image icon;
     std::string package_name;
     std::string activity_name;
   };
 
   using ShowIntentPickerCallback = base::Callback<void(
       content::WebContents* web_contents,
       const std::vector<AppInfo>& app_info,
-      const base::Callback<void(std::string, CloseReason)>& cb)>;
+      const base::Callback<void(const std::string&, CloseReason)>& cb)>;
   ArcNavigationThrottle(content::NavigationHandle* navigation_handle,
                         const ShowIntentPickerCallback& show_intent_picker_cb);
   ~ArcNavigationThrottle() override;
 
   static bool ShouldOverrideUrlLoadingForTesting(const GURL& previous_url,
                                                  const GURL& current_url);
 
  private:
   // content::Navigation implementation:
   NavigationThrottle::ThrottleCheckResult WillStartRequest() override;
   NavigationThrottle::ThrottleCheckResult WillRedirectRequest() override;
 
   NavigationThrottle::ThrottleCheckResult HandleRequest();
   void OnAppCandidatesReceived(
       mojo::Array<mojom::IntentHandlerInfoPtr> handlers);
   void OnAppIconsReceived(
       mojo::Array<mojom::IntentHandlerInfoPtr> handlers,
       std::unique_ptr<ActivityIconLoader::ActivityToIconsMap> icons);
   void OnIntentPickerClosed(mojo::Array<mojom::IntentHandlerInfoPtr> handlers,
-                            std::string selected_app_package,
+                            const std::string& selected_app_package,
                             CloseReason close_reason);
   // A callback object that allow us to display an IntentPicker when Run() is
   // executed, it also allow us to report the user's selection back to
   // OnIntentPickerClosed().
   ShowIntentPickerCallback show_intent_picker_callback_;
 
   // A cache of the action the user took the last time this navigation throttle
   // popped up the intent picker dialog.  If the dialog has never been popped up
   // before, this will have a value of CloseReason::INVALID.  Used to avoid
   // popping up the dialog multiple times on chains of multiple redirects.
   CloseReason previous_user_action_;
 
   // This has to be the last member of the class.
   base::WeakPtrFactory<ArcNavigationThrottle> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcNavigationThrottle);
 };
 
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_NAVIGATION_THROTTLE_H_