Add CertIssuerSource interface and CertIssuerSourceStatic implementation.

net/cert/internal/completion_status.h

Index: net/cert/internal/completion_status.h
diff --git a/net/cert/internal/completion_status.h b/net/cert/internal/completion_status.h
new file mode 100644
index 0000000000000000000000000000000000000000..69126cd601071c0f6c95fbe78562f5d5a0badc7b
--- /dev/null
+++ b/net/cert/internal/completion_status.h
@@ -0,0 +1,17 @@
+// Copyright 2016 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.
+
+#ifndef NET_CERT_INTERNAL_COMPLETION_STATUS_H_
+#define NET_CERT_INTERNAL_COMPLETION_STATUS_H_
+
+namespace net {
+
+enum class CompletionStatus {
+  SYNC,
+  ASYNC,
+};
+
+}  // namespace net
+
+#endif  // NET_CERT_INTERNAL_COMPLETION_STATUS_H_