Add a Model to the download component.

components/download/internal/entry.cc

Index: components/download/internal/entry.cc
diff --git a/components/download/internal/entry.cc b/components/download/internal/entry.cc
new file mode 100644
index 0000000000000000000000000000000000000000..56d819c39d8ddff020472169a73a617d611408d4
--- /dev/null
+++ b/components/download/internal/entry.cc
@@ -0,0 +1,13 @@
+// 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 "components/download/internal/entry.h"
+
+namespace download {
+
+Entry::Entry() = default;
+Entry::Entry(const Entry& other) = default;
+Entry::~Entry() = default;
+
+}  // namespace download