Update translation units for style guide.

impeller/archivist/BUILD.gn

@@ -11,7 +11,10 @@ impeller_component("archivist") {
   public = [ "archive.h" ]
 
   sources = [
+    "archivable.cc",
+    "archivable.h",
     "archive.cc",
+    "archive.h",
     "archive_class_registration.cc",
     "archive_class_registration.h",
     "archive_database.cc",

impeller/archivist/archivable.cc

@@ -0,0 +1,11 @@
+// Copyright 2013 The Flutter 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 "impeller/archivist/archivable.h"
+
+namespace impeller {
+
+//
+
+}  // namespace impeller

impeller/archivist/archivable.h

@@ -0,0 +1,28 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#pragma once
+
+#include <cstdint>
+
+namespace impeller {
+
+class ArchiveLocation;
+
+//------------------------------------------------------------------------------
+/// @brief      Instances of `Archivable`s can be read from and written to a
+///             persistent archive.
+///
+class Archivable {
+ public:
+  using ArchiveName = uint64_t;
+
+  virtual ArchiveName GetArchiveName() const = 0;
+
+  virtual bool Write(ArchiveLocation& item) const = 0;
+
+  virtual bool Read(ArchiveLocation& item) = 0;
+};
+
+}  // namespace impeller