[Sync] Move snapshot cache from SBHI to PSS.

components/browser_sync/profile_sync_service.h

Index: components/browser_sync/profile_sync_service.h
diff --git a/components/browser_sync/profile_sync_service.h b/components/browser_sync/profile_sync_service.h
index 8aaf07b51960b97230da5229b3fa02dcb1e5b166..43c8f8bb7949c0c5b59a8edc8368ac970b256026 100644
--- a/components/browser_sync/profile_sync_service.h
+++ b/components/browser_sync/profile_sync_service.h
@@ -366,7 +366,7 @@ class ProfileSyncService : public syncer::SyncServiceBase,
           debug_info_listener,
       const std::string& cache_guid,
       bool success) override;
-  void OnSyncCycleCompleted() override;
+  void OnSyncCycleCompleted(const syncer::SyncCycleSnapshot& snapshot) override;
   void OnProtocolEvent(const syncer::ProtocolEvent& event) override;
   void OnDirectoryTypeCommitCounterUpdated(
       syncer::ModelType type,
@@ -770,6 +770,9 @@ class ProfileSyncService : public syncer::SyncServiceBase,
   // user.
   GoogleServiceAuthError last_auth_error_;
 
+  // Cache of the last SyncCycleSnapshot received from the sync engine.
+  syncer::SyncCycleSnapshot last_snapshot_;
+
   // Was the last SYNC_PASSPHRASE_REQUIRED notification sent because it
   // was required for encryption, decryption with a cached passphrase, or
   // because a new passphrase is required?