[GCM] Unrevert initial GCM patch

google_apis/gcm/base/gcm_export.h

Index: google_apis/gcm/base/gcm_export.h
diff --git a/google_apis/gcm/base/gcm_export.h b/google_apis/gcm/base/gcm_export.h
new file mode 100644
index 0000000000000000000000000000000000000000..b66eb8e54cfa6735a7c557767e724df8b1ea6c81
--- /dev/null
+++ b/google_apis/gcm/base/gcm_export.h
@@ -0,0 +1,29 @@
+// 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 GOOGLE_APIS_GCM_GCM_EXPORT_H_
+#define GOOGLE_APIS_GCM_GCM_EXPORT_H_
+
+#if defined(COMPONENT_BUILD)
+#if defined(WIN32)
+
+#if defined(GCM_IMPLEMENTATION)
+#define GCM_EXPORT __declspec(dllexport)
+#else
+#define GCM_EXPORT __declspec(dllimport)
+#endif  // defined(GCM_IMPLEMENTATION)
+
+#else  // defined(WIN32)
+#if defined(GCM_IMPLEMENTATION)
+#define GCM_EXPORT __attribute__((visibility("default")))
+#else
+#define GCM_EXPORT
+#endif  // defined(GCM_IMPLEMENTATION)
+#endif
+
+#else  // defined(COMPONENT_BUILD)
+#define GCM_EXPORT
+#endif
+
+#endif  // GOOGLE_APIS_GCM_GCM_EXPORT_H_