Make the rest of the services have a similar raw/user interface structure.

service/memcache/raw_interface.go

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package memcache
+
+// RawCB is a simple error callback for most of the methods in RawInterface.
+type RawCB func(error)
+
+// RawItemCB is the callback for RawInterface.GetMulti. It takes the retrieved
+// item and the error for that item (e.g. ErrCacheMiss) if there was one..
+type RawItemCB func(Item, error)
+
+// RawInterface is the full interface to the memcache service.
+type RawInterface interface {
+        NewItem(key string) Item
+
+        AddMulti(items []Item, cb RawCB) error
+        SetMulti(items []Item, cb RawCB) error
+        GetMulti(keys []string, cb RawItemCB) error
+        DeleteMulti(keys []string, cb RawCB) error
+        CompareAndSwapMulti(items []Item, cb RawCB) error
+
+        Increment(key string, delta int64, initialValue *uint64) (newValue uint64, err error)
+
+        Flush() error
+
+        Stats() (*Statistics, error)
+}