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

chrome/browser/ui/views/webshare/webshare_target_picker_view_unittest.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 <string>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 65 matching lines @@
 
   // The view under test.
   WebShareTargetPickerView* view() { return view_; }
   // The table inside the view (for inspection).
   views::TableView* table() { return view_->table_; }
 
   // The result that was returned to the dialog's callback.
   const base::Optional<std::string>& result() { return result_; }
 
  private:
-  void OnCallback(base::Optional<std::string> result) {
+  void OnCallback(const base::Optional<std::string>& result) {
     result_ = result;
     if (quit_closure_)
       quit_closure_.Run();
   }
 
   std::unique_ptr<views::Widget> parent_widget_;
   WebShareTargetPickerView* view_ = nullptr;
 
   base::Optional<std::string> result_;
 
@@ skipping 67 matching lines @@
   base::RunLoop run_loop;
   SetQuitClosure(run_loop.QuitClosure());
 
   view()->OnDoubleClick();
 
   run_loop.Run();
 
   EXPECT_EQ(base::Optional<std::string>("https://appone.com/path/bits"),
             result());
 }