Add ContentSuggestion, ContentSuggestionCategory and ContentSuggestionProviderType

components/ntp_snippets/content_suggestion_category.h

Index: components/ntp_snippets/content_suggestion_category.h
diff --git a/components/ntp_snippets/content_suggestion_category.h b/components/ntp_snippets/content_suggestion_category.h
new file mode 100644
index 0000000000000000000000000000000000000000..80268fbe1405ca4c8dc48ac516c5536c57997a3f
--- /dev/null
+++ b/components/ntp_snippets/content_suggestion_category.h
@@ -0,0 +1,18 @@
+// 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.
+
+#ifndef COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTION_CATEGORY_H_
+#define COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTION_CATEGORY_H_
+
+namespace ntp_snippets {
+
+// The category of a content suggestion. Note that even though these categories
+// currently match the provider types, a provider type is not limited to provide
+// suggestions of a single (fixed) category only. The category is used to
+// determine where to display the suggestion.
+enum class ContentSuggestionCategory : int { ARTICLE };
+
+}  // namespace ntp_snippets
+
+#endif  // COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTION_CATEGORY_H_