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

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

 // 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.
 
 #include "chrome/browser/ui/views/webshare/webshare_target_picker_view.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/ui/views/harmony/chrome_layout_provider.h"
 #include "chrome/grit/generated_resources.h"
 #include "components/constrained_window/constrained_window_views.h"
@@ skipping 48 matching lines @@
                            ")");
 }
 
 void TargetPickerTableModel::SetObserver(ui::TableModelObserver* observer) {}
 
 namespace chrome {
 
 void ShowWebShareTargetPickerDialog(
     gfx::NativeWindow parent_window,
     const std::vector<std::pair<base::string16, GURL>>& targets,
-    const base::Callback<void(base::Optional<std::string>)>& callback) {
+    const chrome::WebShareTargetPickerCallback& callback) {
   constrained_window::CreateBrowserModalDialogViews(
       new WebShareTargetPickerView(targets, callback), parent_window)
       ->Show();
 }
 
 }  // namespace chrome
 
 WebShareTargetPickerView::WebShareTargetPickerView(
     const std::vector<std::pair<base::string16, GURL>>& targets,
-    const base::Callback<void(base::Optional<std::string>)>& close_callback)
+    const chrome::WebShareTargetPickerCallback& close_callback)
     : targets_(targets),
       table_model_(base::MakeUnique<TargetPickerTableModel>(&targets_)),
       close_callback_(close_callback) {
   const int panel_margin = ChromeLayoutProvider::Get()->GetDistanceMetric(
       DISTANCE_PANEL_CONTENT_MARGIN);
   views::BoxLayout* layout =
       new views::BoxLayout(views::BoxLayout::kVertical, panel_margin,
                            panel_margin, views::kRelatedControlVerticalSpacing);
   SetLayoutManager(layout);
 
@@ skipping 70 matching lines @@
   return true;
 }
 
 void WebShareTargetPickerView::OnSelectionChanged() {
   GetDialogClientView()->UpdateDialogButtons();
 }
 
 void WebShareTargetPickerView::OnDoubleClick() {
   GetDialogClientView()->AcceptWindow();
 }