Refactor a bit.

service/info/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 info
+
+import (
+        "time"
+
+        "golang.org/x/net/context"
+)
+
+// Interface is the interface for all of the package methods which normally
+// would be in the 'appengine' package.
+type Interface interface {
+        AppID() string
+        Datacenter() string
+        DefaultVersionHostname() string
+        InstanceID() string
+        IsDevAppServer() bool
+        IsOverQuota(err error) bool
+        IsTimeoutError(err error) bool
+        ModuleHostname(module, version, instance string) (string, error)
+        ModuleName() string
+        RequestID() string
+        ServerSoftware() string
+        ServiceAccount() (string, error)
+        VersionID() string
+
+        Namespace(namespace string) (context.Context, error)
+
+        AccessToken(scopes ...string) (token string, expiry time.Time, err error)
+        PublicCertificates() ([]Certificate, error)
+        SignBytes(bytes []byte) (keyName string, signature []byte, err error)
+}