Add #ifndef guards to cef_export.h (issue #375).

git-svn-id: https://chromiumembedded.googlecode.com/svn/trunk@311 5089003a-bbd8-11dd-ad1f-f1f9622dbc98

include/internal/cef_export.h

@@ -28,6 +28,9 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+#ifndef _CEF_EXPORT_H
+#define _CEF_EXPORT_H
+
 #include "cef_build.h"
 
 #if defined(COMPILER_MSVC)
@@ -47,3 +50,5 @@
 #define CEF_CALLBACK
 
 #endif  // COMPILER_GCC
+
+#endif // _CEF_EXPORT_H