[sync] Componentize sync: Part Final: Target 'sync' is now its own component

sync/base/sync_export.h

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Copyright 2013 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 SYNC_SYNC_EXPORT_H_
 #define SYNC_SYNC_EXPORT_H_
 
-// TODO(akalin): Remove '0 && ' when sync becomes a component.
-#if 0 && defined(COMPONENT_BUILD)
+// Notes:
+// 1) To make a symbol accessible from 'sync_unit_tests', but hidden from
+//    chrome components like 'browser', or from chrome test suites like
+//    'unit_tests' or 'sync_integration_tests', use SYNC_EXPORT_PRIVATE.
+// 2) To make a symbol accessible from chrome components, chrome test suites,
+//    and 'sync_unit_tests', use SYNC_EXPORT.
+// 3) Typically, if you need to add a 'sync/*' entry to a DEPS file outside
+//    'sync/', you will also need to export the class being used. Otherwise, you
+//    may see linker errors with a component build.
+// See http://www.chromium.org/developers/how-tos/component-build for more info.
+// TODO(rsimha): Include a link to a doc on sync componentization.

[Ryan Sleevi, 2013/01/23 04:06:21]

Is this comment necessary? Does it deviate at all from the 'normal'
componentization process?

It seems like this is just the same old API.

[Raghu Simha, 2013/01/23 08:04:06]

This is the same API as the other FOO_EXPORTs. Tim asked me to add a comment
here to help folks debug link errors. If you think this seems repetitive, I'll
let folks know offline.

+
+#if defined(COMPONENT_BUILD)
 #if defined(WIN32)
 
 #if defined(SYNC_IMPLEMENTATION)
 #define SYNC_EXPORT __declspec(dllexport)
 #define SYNC_EXPORT_PRIVATE __declspec(dllexport)
 #elif defined(SYNC_TEST)
 #define SYNC_EXPORT __declspec(dllimport)
 #define SYNC_EXPORT_PRIVATE __declspec(dllimport)
 #else
 #define SYNC_EXPORT __declspec(dllimport)
@@ skipping 12 matching lines @@
 #define SYNC_EXPORT_PRIVATE
 #endif  // defined(SYNC_IMPLEMENTATION)
 #endif
 
 #else  // defined(COMPONENT_BUILD)
 #define SYNC_EXPORT
 #define SYNC_EXPORT_PRIVATE
 #endif
 
 #endif  // SYNC_SYNC_EXPORT_H_