Implement Mail service.

filter/count/mail.go

Index: filter/count/mail.go
diff --git a/filter/count/mail.go b/filter/count/mail.go
new file mode 100644
index 0000000000000000000000000000000000000000..01fc98691071e9a509c21663acfcf197214c67a6
--- /dev/null
+++ b/filter/count/mail.go
@@ -0,0 +1,44 @@
+// 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 count
+
+import (
+	"github.com/luci/gae/service/mail"
+	"golang.org/x/net/context"
+)
+
+// MailCounter is the counter object for the Mail service.
+type MailCounter struct {
+	Send         Entry
+	SendToAdmins Entry
+}
+
+type mailCounter struct {
+	c *MailCounter
+
+	m mail.Interface
+}
+
+var _ mail.Interface = (*mailCounter)(nil)
+
+func (m *mailCounter) Send(msg *mail.Message) error {
+	return m.c.Send.up(m.m.Send(msg))
+}
+
+func (m *mailCounter) SendToAdmins(msg *mail.Message) error {
+	return m.c.SendToAdmins.up(m.m.SendToAdmins(msg))
+}
+
+func (m *mailCounter) Testable() mail.Testable {
+	return m.m.Testable()
+}
+
+// FilterMail installs a counter Mail filter in the context.
+func FilterMail(c context.Context) (context.Context, *MailCounter) {
+	state := &MailCounter{}
+	return mail.AddFilters(c, func(ic context.Context, u mail.Interface) mail.Interface {
+		return &mailCounter{state, u}
+	}), state
+}