Move testing file which contains keysmith response to export/sdk/testing.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=221487408

common/certificate_type.h

@@ -0,0 +1,22 @@
+////////////////////////////////////////////////////////////////////////////////
+// Copyright 2017 Google LLC.
+//
+// This software is licensed under the terms defined in the Widevine Master
+// License Agreement. For a copy of this agreement, please contact
+// widevine-licensing@google.com.
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef COMMON_CERTIFICATE_TYPE_H_
+#define COMMON_CERTIFICATE_TYPE_H_
+
+namespace widevine {
+
+enum CertificateType {
+  kCertificateTypeTesting,
+  kCertificateTypeDevelopment,
+  kCertificateTypeProduction,
+};
+
+}  // namespace widevine
+
+#endif  // COMMON_CERTIFICATE_TYPE_H_