Pass user session type to extension feature checks

extensions/common/features/feature_session_type.cc

Index: extensions/common/features/feature_session_type.cc
diff --git a/extensions/common/features/feature_session_type.cc b/extensions/common/features/feature_session_type.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e81595dc009fc26a332e2b27a855237ce26c4cdb
--- /dev/null
+++ b/extensions/common/features/feature_session_type.cc
@@ -0,0 +1,39 @@
+// Copyright 2016 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 "extensions/common/features/feature_session_type.h"
+
+#include "base/logging.h"
+
+namespace {
+
+const extensions::FeatureSessionType kDefaultSessionType =

[Devlin, 2016/08/18 17:19:15]

I think this variable is probably unnecessary.

[tbarzic, 2016/08/18 18:58:10]

It's used to test whether the value has changed from the default one.

+    extensions::FEATURE_SESSION_TYPE_UNKNOWN;
+extensions::FeatureSessionType g_current_session_type = kDefaultSessionType;

[Devlin, 2016/08/18 17:19:15]

Just put the anonymous namespace inside the extensions namespace so we don't
have extensions::.

[tbarzic, 2016/08/18 18:58:10]

Done.

+
+}  // namespace
+
+namespace extensions {
+
+FeatureSessionType GetCurrentFeatureSessionType() {
+  return g_current_session_type;
+}
+
+void SetCurrentFeatureSessionType(FeatureSessionType session_type) {
+  CHECK(g_current_session_type == kDefaultSessionType ||
+        session_type == g_current_session_type);

[Devlin, 2016/08/18 17:19:15]

I'm assuming the motivation here is to not let the session type be set more than
once?  Maybe add a comment if that's the case?

[tbarzic, 2016/08/18 18:58:10]

Added a comment.

+  g_current_session_type = session_type;
+}
+
+ScopedCurrentFeatureSessionType::ScopedCurrentFeatureSessionType(
+    FeatureSessionType session_type) {
+  original_session_type_ = GetCurrentFeatureSessionType();
+  SetCurrentFeatureSessionType(session_type);
+}
+
+ScopedCurrentFeatureSessionType::~ScopedCurrentFeatureSessionType() {
+  g_current_session_type = original_session_type_;
+}
+
+}  // namespace extensions