Flush Channel IDs when Cookies get saved to a persistent backend

net/ssl/default_channel_id_store_unittest.cc

Index: net/ssl/default_channel_id_store_unittest.cc
diff --git a/net/ssl/default_channel_id_store_unittest.cc b/net/ssl/default_channel_id_store_unittest.cc
index 9408d6eebf9fdf5eca25f11a0bc1218d897fec28..986161b0309c040486d32812ee24ca134dab5dfb 100644
--- a/net/ssl/default_channel_id_store_unittest.cc
+++ b/net/ssl/default_channel_id_store_unittest.cc
@@ -80,6 +80,7 @@ class MockPersistentStore
   void DeleteChannelID(
       const DefaultChannelIDStore::ChannelID& channel_id) override;
   void SetForceKeepSessionState() override;
+  void Flush() override;
 
  protected:
   ~MockPersistentStore() override;
@@ -121,6 +122,8 @@ void MockPersistentStore::DeleteChannelID(
 
 void MockPersistentStore::SetForceKeepSessionState() {}
 
+void MockPersistentStore::Flush() {}
+
 MockPersistentStore::~MockPersistentStore() {}
 
 bool DomainEquals(const std::string& domain1, const std::string& domain2) {