Revert of Mojo: Eliminate duplicate C API symbols

mojo/public/platform/native/thunk_export.h

Index: mojo/public/platform/native/thunk_export.h
diff --git a/mojo/public/platform/native/thunk_export.h b/mojo/public/platform/native/thunk_export.h
new file mode 100644
index 0000000000000000000000000000000000000000..4ec7c85b046a19a3c4ba26ddbab042c198216f31
--- /dev/null
+++ b/mojo/public/platform/native/thunk_export.h
@@ -0,0 +1,18 @@
+// Copyright 2014 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 MOJO_PUBLIC_PLATFORM_NATIVE_THUNK_EXPORT_H_
+#define MOJO_PUBLIC_PLATFORM_NATIVE_THUNK_EXPORT_H_
+
+// Call this function by looking inside the resulting shared object and
+// grabbing the symbol manually.
+//
+// Always export this api.
+#if defined(WIN32)
+#define THUNK_EXPORT __declspec(dllexport)
+#else
+#define THUNK_EXPORT __attribute__((visibility("default")))
+#endif
+
+#endif // MOJO_PUBLIC_PLATFORM_NATIVE_THUNK_EXPORT_H_