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..7d358615a2709c481de874a4c2e2fea93275ade7
--- /dev/null
+++ b/extensions/common/features/feature_session_type.cc
@@ -0,0 +1,36 @@
+// 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"
+#include "base/memory/ptr_util.h"
+
+namespace extensions {
+
+namespace {
+
+const FeatureSessionType kDefaultSessionType = FeatureSessionType::UNKNOWN;
+FeatureSessionType g_current_session_type = kDefaultSessionType;
+
+}  // namespace
+
+FeatureSessionType GetCurrentFeatureSessionType() {
+  return g_current_session_type;
+}
+
+void SetCurrentFeatureSessionType(FeatureSessionType session_type) {
+  // Make sure that session type stays constants after it's been initialized.

[Devlin, 2016/08/19 00:43:28]

It's not really that it stays constant in the case of a
ScopedCurrentFeatureSessionType going out of scope, right?  e.g. in a test with
multiple Scoped overrides?

(Also, this check is another reason that the unset vs other distinction is
important)

[tbarzic, 2016/08/19 17:23:32]

Yeah, it may be different in tests, but that's kinda the point of
ScopedCurrenteaturesSessionType.

+  CHECK(g_current_session_type == kDefaultSessionType ||
+        session_type == g_current_session_type);
+  g_current_session_type = session_type;
+}
+
+std::unique_ptr<base::AutoReset<FeatureSessionType>>
+ScopedCurrentFeatureSessionType(FeatureSessionType type) {
+  return base::MakeUnique<base::AutoReset<FeatureSessionType>>(
+      &g_current_session_type, type);
+}
+
+}  // namespace extensions