Add ContentSuggestion, ContentSuggestionCategory and ContentSuggestionProviderType

components/ntp_snippets/ntp_snippet.h

Index: components/ntp_snippets/ntp_snippet.h
diff --git a/components/ntp_snippets/ntp_snippet.h b/components/ntp_snippets/ntp_snippet.h
index 745c246e9d619f3c6c390da482d41d776d5dbf3e..fb7d64241bdff8f0cc11b4a1bcd7ae912c86d368 100644
--- a/components/ntp_snippets/ntp_snippet.h
+++ b/components/ntp_snippets/ntp_snippet.h
@@ -11,6 +11,7 @@
 
 #include "base/macros.h"
 #include "base/time/time.h"
+#include "components/ntp_snippets/snippet.h"
 #include "url/gurl.h"
 
 namespace base {
@@ -125,6 +126,8 @@ class NTPSnippet {
   bool is_discarded() const { return is_discarded_; }
   void set_discarded(bool discarded) { is_discarded_ = discarded; }
 
+  std::unique_ptr<Snippet> ToSnippet() const;
+
   // Public for testing.
   static base::Time TimeFromJsonString(const std::string& timestamp_str);
   static std::string TimeToJsonString(const base::Time& time);