[NTP Snippets] Persist snippets in a LevelDB instead of prefs

components/ntp_snippets/proto/BUILD.gn

Index: components/ntp_snippets/proto/BUILD.gn
diff --git a/components/autofill/core/browser/proto/BUILD.gn b/components/ntp_snippets/proto/BUILD.gn
similarity index 90%
copy from components/autofill/core/browser/proto/BUILD.gn
copy to components/ntp_snippets/proto/BUILD.gn
index ad52e78646b3a2edf44ea16e992e3d8187eb2dad..95ba179662570ba5a461f1b9c9f060babb058eaa 100644
--- a/components/autofill/core/browser/proto/BUILD.gn
+++ b/components/ntp_snippets/proto/BUILD.gn
@@ -6,6 +6,6 @@ import("//third_party/protobuf/proto_library.gni")
 
 proto_library("proto") {
   sources = [
-    "server.proto",
+    "ntp_snippets.proto",
   ]
 }