[NTP] Upload file from the most recent directory

By setting the last selected directory to the user profile after the
user select a custom background image, the user can go to the last
directory instead of going to "This PC" or home directory.

Bugs: 867758
Change-Id: I6b6fb1296a2f1ffb60148522cdd25a1f027f630e
Reviewed-on: https://chromium-review.googlesource.com/1162712Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Commit-Queue: Weilun Shi <sweilun@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580921}

chrome/browser/ui/search/search_tab_helper.cc

@@ -405,8 +405,10 @@ void SearchTabHelper::OnSetCustomBackgroundURLWithAttributions(
 void SearchTabHelper::FileSelected(const base::FilePath& path,
                                    int index,
                                    void* params) {
-  if (instant_service_)
+  if (instant_service_) {
+    profile()->set_last_selected_directory(path.DirName());
     instant_service_->SelectLocalBackgroundImage(path);
+  }
 
   select_file_dialog_ = nullptr;
 }