webshare: Small refactor of WebShare (OnceCallback, const&, and alias)

chrome/browser/ui/views/webshare/webshare_target_picker_view.h

 // Copyright 2017 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_UI_VIEWS_WEBSHARE_WEBSHARE_TARGET_PICKER_VIEW_H_
 #define CHROME_BROWSER_UI_VIEWS_WEBSHARE_WEBSHARE_TARGET_PICKER_VIEW_H_
 
 #include <vector>
 
 #include "base/callback.h"
@@ skipping 20 matching lines @@
 // used by any released code until going through UI review.
 class WebShareTargetPickerView : public views::DialogDelegateView,
                                  public views::TableViewObserver {
  public:
   // |targets| is a list of app title and manifest URL pairs that will be shown
   // in a list. If the user picks a target, this calls |callback| with the
   // manifest URL of the chosen target, or returns null if the user cancelled
   // the share.
   WebShareTargetPickerView(
       const std::vector<std::pair<base::string16, GURL>>& targets,
-      const base::Callback<void(base::Optional<std::string>)>&
-          close_callback);
+      chrome::WebShareTargetPickerCallback close_callback);
   ~WebShareTargetPickerView() override;
 
   // views::View overrides:
   gfx::Size GetPreferredSize() const override;
 
   // views::WidgetDelegate overrides:
   ui::ModalType GetModalType() const override;
   base::string16 GetWindowTitle() const override;
 
   // views::DialogDelegate overrides:
   bool Cancel() override;
   bool Accept() override;
   base::string16 GetDialogButtonLabel(ui::DialogButton button) const override;
   bool IsDialogButtonEnabled(ui::DialogButton button) const override;
 
   // views::TableViewObserver overrides:
   void OnSelectionChanged() override;
   void OnDoubleClick() override;
 
  private:
   // For access to |table_|.
   friend class WebShareTargetPickerViewTest;
 
   views::TableView* table_ = nullptr;
 
   const std::vector<std::pair<base::string16, GURL>> targets_;
   std::unique_ptr<TargetPickerTableModel> table_model_;
 
-  base::Callback<void(base::Optional<std::string>)> close_callback_;
+  chrome::WebShareTargetPickerCallback close_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(WebShareTargetPickerView);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_WEBSHARE_WEBSHARE_TARGET_PICKER_VIEW_H_