Replace base::NullableString16(bool) usage with default constructor.

content/browser/web_contents/web_drag_dest_gtk.cc

 // Copyright (c) 2012 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 "content/browser/web_contents/web_drag_dest_gtk.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
@@ skipping 191 matching lines @@
           GURL url(*uri_iter);
           base::FilePath file_path;
           if (url.SchemeIs(chrome::kFileScheme) &&
               net::FileURLToFilePath(url, &file_path)) {
             drop_data_->filenames.push_back(
                 WebDropData::FileInfo(UTF8ToUTF16(file_path.value()),
                                       string16()));
             // This is a hack. Some file managers also populate text/plain with
             // a file URL when dragging files, so we clear it to avoid exposing
             // it to the web content.
-            drop_data_->text = base::NullableString16(true);
+            drop_data_->text = base::NullableString16();
           } else if (!drop_data_->url.is_valid()) {
             // Also set the first non-file URL as the URL content for the drop.
             drop_data_->url = url;
           }
         }
         g_strfreev(uris);
       }
     } else if (target == ui::GetAtomForTarget(ui::TEXT_HTML)) {
       // TODO(estade): Can the html have a non-UTF8 encoding?
       drop_data_->html = base::NullableString16(
@@ skipping 107 matching lines @@
   gtk_drag_finish(context, is_drop_target_, FALSE, time);
 
   return TRUE;
 }
 
 RenderViewHostImpl* WebDragDestGtk::GetRenderViewHost() const {
   return static_cast<RenderViewHostImpl*>(web_contents_->GetRenderViewHost());
 }
 
 }  // namespace content