predictors: Refactor Glowplug Database.

All Glowplug tables have the same structure. A table has two columns
representing string as a key and protobuf message as a value.

The goal of this refactor is to ease adding new tables in Glowplug and reduce
amount of the code. This CL also makes easier a replacement of database backend.

Bug: 715525
Change-Id: Idc16a81b91b3d9576454839bceaa602db4b3f354
Reviewed-on: https://chromium-review.googlesource.com/506087
Commit-Queue: Alexandr Ilin <[email protected]>
Reviewed-by: Benoit L <[email protected]>
Cr-Commit-Position: refs/heads/master@{#475500}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 58f30f86..64976c5 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -974,6 +974,7 @@
     "predictors/autocomplete_action_predictor_factory.h",
     "predictors/autocomplete_action_predictor_table.cc",
     "predictors/autocomplete_action_predictor_table.h",
+    "predictors/glowplug_key_value_data.h",
     "predictors/glowplug_key_value_table.cc",
     "predictors/glowplug_key_value_table.h",
     "predictors/loading_predictor.cc",