Improve code style.

Change-Id: I26e043849bce2a4b41ae132fbe0c882f4a6f112f
diff --git a/slang_diagnostic_buffer.h b/slang_diagnostic_buffer.h
index cadbeab..3c4e1c7 100644
--- a/slang_diagnostic_buffer.h
+++ b/slang_diagnostic_buffer.h
@@ -14,14 +14,14 @@
  * limitations under the License.
  */
 
-#ifndef _SLANG_COMPILER_DIAGNOSTIC_BUFFER_H
-#define _SLANG_COMPILER_DIAGNOSTIC_BUFFER_H
+#ifndef _FRAMEWORKS_COMPILE_SLANG_SLANG_DIAGNOSTIC_BUFFER_H_  // NOLINT
+#define _FRAMEWORKS_COMPILE_SLANG_SLANG_DIAGNOSTIC_BUFFER_H_
 
-#include "llvm/Support/raw_ostream.h"
+#include <string>
 
 #include "clang/Basic/Diagnostic.h"
 
-#include <string>
+#include "llvm/Support/raw_ostream.h"
 
 namespace llvm {
   class raw_string_ostream;
@@ -55,4 +55,4 @@
 };
 }
 
-#endif  // _SLANG_DIAGNOSTIC_BUFFER_H
+#endif  // _FRAMEWORKS_COMPILE_SLANG_SLANG_DIAGNOSTIC_BUFFER_H_  NOLINT