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

chrome/browser/webshare/share_service_impl.cc

Index: chrome/browser/webshare/share_service_impl.cc
diff --git a/chrome/browser/webshare/share_service_impl.cc b/chrome/browser/webshare/share_service_impl.cc
index 4aca48813cb7b9e3b798b387f6a54bfa1d24fcf9..6c1a15b73e0c104169b860929bf40289be05e191 100644
--- a/chrome/browser/webshare/share_service_impl.cc
+++ b/chrome/browser/webshare/share_service_impl.cc
@@ -104,8 +104,8 @@ bool ShareServiceImpl::ReplacePlaceholders(base::StringPiece url_template,
 
 void ShareServiceImpl::ShowPickerDialog(
     const std::vector<std::pair<base::string16, GURL>>& targets,
-    const base::Callback<void(base::Optional<std::string>)>& callback) {
-// TODO(mgiuca): Get the browser window as |parent_window|.
+    const chrome::WebShareTargetPickerCallback& callback) {
+  // TODO(mgiuca): Get the browser window as |parent_window|.
   chrome::ShowWebShareTargetPickerDialog(nullptr /* parent_window */, targets,
                                          callback);
 }
@@ -197,7 +197,7 @@ void ShareServiceImpl::OnPickerClosed(
     const std::string& text,
     const GURL& share_url,
     const ShareCallback& callback,
-    base::Optional<std::string> result) {
+    const base::Optional<std::string>& result) {
   if (!result.has_value()) {
     callback.Run(blink::mojom::ShareError::CANCELED);
     return;