Extensions: Pass current channel and feature session type to extension unpack utility process.

extensions/common/extension_unpacker.typemap

Index: extensions/common/extension_unpacker.typemap
diff --git a/extensions/common/extension_unpacker.typemap b/extensions/common/extension_unpacker.typemap
new file mode 100644
index 0000000000000000000000000000000000000000..f95195990a6bdaa613fdcea3129fd0bd33d0a79f
--- /dev/null
+++ b/extensions/common/extension_unpacker.typemap
@@ -0,0 +1,23 @@
+# 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.
+
+mojom = "//extensions/common/extension_unpacker.mojom"
+
+public_headers = [
+  "//extensions/common/manifest.h",
+  "//extensions/common/features/feature_session_type.h",
+  "//components/version_info/version_info.h",
+]
+
+traits_headers = [
+  "//extensions/common/manifest_location_param_traits.h",
+  "//extensions/common/feature_channel_param_traits.h",
+  "//extensions/common/feature_session_type_param_traits.h",
+]
+
+type_mappings = [
+  "extensions.mojom.ManifestLocation=extensions::Manifest::Location",
+  "extensions.mojom.FeatureChannel=version_info::Channel",
+  "extensions.mojom.FeatureSessionType=extensions::FeatureSessionType",
+]