Delete blimp/helium and remove references to it from dependent targets

blimp/helium/serializable.h

-// 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 BLIMP_HELIUM_SERIALIZABLE_H_
-#define BLIMP_HELIUM_SERIALIZABLE_H_
-
-namespace google {
-namespace protobuf {
-namespace io {
-class CodedInputStream;
-class CodedOutputStream;
-}  // namespace io
-}  // namespace protobuf
-}  // namespace google
-
-namespace blimp {
-namespace helium {
-
-// Defines methods needed to serialize and deserialize |this| from a byte
-// stream.
-class Serializable {
- public:
-  virtual void Serialize(
-      google::protobuf::io::CodedOutputStream* output_stream) const = 0;
-  virtual bool Parse(google::protobuf::io::CodedInputStream* input_stream) = 0;
-};
-
-}  // namespace helium
-}  // namespace blimp
-
-#endif  // BLIMP_HELIUM_SERIALIZABLE_H_