Implement Mail service.

filter/featureBreaker/mail.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 featureBreaker
+
+import (
+        "github.com/luci/gae/service/mail"
+        "golang.org/x/net/context"
+)
+
+type mailState struct {
+        *state
+
+        mail.Interface
+}
+
+var _ mail.Interface = (*mailState)(nil)
+
+func (m *mailState) Send(msg *mail.Message) error {
+        return m.run(func() error { return m.Interface.Send(msg) })
+}
+
+func (m *mailState) SendToAdmins(msg *mail.Message) error {
+        return m.run(func() error { return m.Interface.SendToAdmins(msg) })
+}
+
+// FilterMail installs a counter mail filter in the context.
+func FilterMail(c context.Context, defaultError error) (context.Context, FeatureBreaker) {
+        state := newState(defaultError)
+        return mail.AddFilters(c, func(ic context.Context, i mail.Interface) mail.Interface {
+                return &mailState{state, i}
+        }), state
+}