[USS] Implement GetAllData and GetStorageKey.

components/history/core/browser/history_backend.h

Index: components/history/core/browser/history_backend.h
diff --git a/components/history/core/browser/history_backend.h b/components/history/core/browser/history_backend.h
index 59c58389c1294a9e956c3e76b35e0a53240313c8..761fdcd42d4dfcc1c8e51d2aa65818a1f788928b 100644
--- a/components/history/core/browser/history_backend.h
+++ b/components/history/core/browser/history_backend.h
@@ -32,6 +32,7 @@
 #include "components/history/core/browser/history_types.h"
 #include "components/history/core/browser/keyword_id.h"
 #include "components/history/core/browser/thumbnail_database.h"
+#include "components/history/core/browser/typed_url_sync_bridge.h"
 #include "components/history/core/browser/visit_tracker.h"
 #include "sql/init_status.h"
 
@@ -53,7 +54,6 @@ struct HistoryDatabaseParams;
 class HistoryDBTask;
 class InMemoryHistoryBackend;
 class TypedUrlSyncableService;
-class TypedURLSyncBridge;
 class HistoryBackendHelper;
 class URLDatabase;
 
@@ -476,6 +476,10 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
   HistoryDatabase* db() const { return db_.get(); }
 
   ExpireHistoryBackend* expire_backend() { return &expirer_; }
+
+  void SetTypedURLSyncBridge(std::unique_ptr<TypedURLSyncBridge> bridge) {

[pavely, 2017/06/01 20:49:18]

Could you name it SetTypedURLSyncBridgeForTest. This is common pattern in
Chromium. Makes usecases of this function obvious.

[Gang Wu, 2017/06/02 00:00:23]

Done.

+    typed_url_sync_bridge_.swap(bridge);

[pavely, 2017/06/01 20:49:18]

I'd prefer "typed_url_sync_bridge_ = std::move(bridge);"
It conveys the intention. Swap would make sense if you were planning to return
old value.

[Gang Wu, 2017/06/02 00:00:23]

Done.

+  }
 #endif
 
   // Returns true if the passed visit time is already expired (used by the sync