[sync] Add typed url sync metadata to the history db

components/history/core/browser/history_database.h

Index: components/history/core/browser/history_database.h
diff --git a/components/history/core/browser/history_database.h b/components/history/core/browser/history_database.h
index 9a26ae981941c1d598e8db459b5c84fb1f5103f1..082b685a940ba5f957485f828892f566982fb955 100644
--- a/components/history/core/browser/history_database.h
+++ b/components/history/core/browser/history_database.h
@@ -13,12 +13,12 @@
 #include "build/build_config.h"
 #include "components/history/core/browser/download_database.h"
 #include "components/history/core/browser/history_types.h"
+#include "components/history/core/browser/typed_url_sync_metadata_database.h"
 #include "components/history/core/browser/url_database.h"
 #include "components/history/core/browser/visit_database.h"
 #include "components/history/core/browser/visitsegment_database.h"
 #include "sql/connection.h"
 #include "sql/init_status.h"
-#include "sql/meta_table.h"
 
 #if defined(OS_ANDROID)
 #include "components/history/core/browser/android/android_cache_database.h"
@@ -45,6 +45,7 @@ class HistoryDatabase : public DownloadDatabase,
                         public AndroidURLsDatabase,
                         public AndroidCacheDatabase,
 #endif
+                        public TypedURLSyncMetadataDatabase,
                         public URLDatabase,
                         public VisitDatabase,
                         public VisitSegmentDatabase {
@@ -191,7 +192,6 @@ class HistoryDatabase : public DownloadDatabase,
   // ---------------------------------------------------------------------------
 
   sql::Connection db_;
-  sql::MetaTable meta_table_;

[brettw, 2017/03/20 17:27:06]

Conceptually, the meta table should live at this layer since it's really a
global history database thing.

The not-so-great inheritance use by the history system is my fault from long ago
that makes this more difficult than it might otherwise be.

The best thing I can think of is if your typed table class had a
set_meta_table(MetaTable* table) member. HistoryDatabase would set this on init
and clear this in it's destructor (to prevent dangling pointers on destruction).
What do you think?

[Gang Wu, 2017/03/20 21:34:47]

I copied idea from db_ and GetDB(), in base class has a virtual class to get
MetaTable, do you think it is ok?

 
   base::Time cached_early_expiration_threshold_;