sync: remove use of protobuf extensions in protocol to reduce static init overhead.

chrome/browser/sync/test/engine/proto_extension_validator.h

-// Copyright (c) 2010 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.
-
-// A test utility that makes it easy to assert the exact presence of
-// protobuf extensions in an extensible message.  Example code:
-//
-// sync_pb::EntitySpecifics value;   // Set up a test value.
-// value.MutableExtension(sync_pb::bookmark);
-//
-// ProtoExtensionValidator<sync_pb::EntitySpecifics> good_expectation(value);
-// good_expectation.ExpectHasExtension(sync_pb::bookmark);
-// good_expectation.ExpectHasNoOtherFieldsOrExtensions();
-//
-// ProtoExtensionValidator<sync_pb::EntitySpecifics> bad_expectation(value);
-// bad_expectation.ExpectHasExtension(sync_pb::preference);  // Fails, no pref
-// bad_expectation.ExpectHasNoOtherFieldsOrExtensions();  // Fails, bookmark
-
-#ifndef CHROME_BROWSER_SYNC_TEST_ENGINE_PROTO_EXTENSION_VALIDATOR_H_
-#define CHROME_BROWSER_SYNC_TEST_ENGINE_PROTO_EXTENSION_VALIDATOR_H_
-#pragma once
-
-#include "base/string_util.h"
-#include "chrome/browser/sync/test/engine/syncer_command_test.h"
-#include "testing/gtest/include/gtest/gtest.h"
-
-namespace browser_sync {
-
-template<typename MessageType>
-class ProtoExtensionValidator {
- public:
-  explicit ProtoExtensionValidator(const MessageType& proto)
-    : proto_(proto) {
-  }
-  template<typename ExtensionTokenType>
-  void ExpectHasExtension(ExtensionTokenType token) {
-    EXPECT_TRUE(proto_.HasExtension(token))
-        << "Proto failed to contain expected extension";
-    proto_.ClearExtension(token);
-    EXPECT_FALSE(proto_.HasExtension(token));
-  }
-  void ExpectNoOtherFieldsOrExtensions() {
-    EXPECT_EQ(MessageType::default_instance().SerializeAsString(),
-              proto_.SerializeAsString())
-        << "Proto contained additional unexpected extensions.";
-  }
-
- private:
-  MessageType proto_;
-  DISALLOW_COPY_AND_ASSIGN(ProtoExtensionValidator);
-};
-
-}  // namespace browser_sync
-
-#endif  // CHROME_BROWSER_SYNC_TEST_ENGINE_PROTO_EXTENSION_VALIDATOR_H_