Add extern "C" for C++ compatibility.

Change-Id: I13369c84fa736e0d38f19480068abfb5dc54dcc8
diff --git a/av1/decoder/inspection.h b/av1/decoder/inspection.h
index 37e7b95..d6098f4 100644
--- a/av1/decoder/inspection.h
+++ b/av1/decoder/inspection.h
@@ -1,6 +1,10 @@
 #ifndef AOM_INSPECTION_H_
 #define AOM_INSPECTION_H_
 
+#ifdef __cplusplus
+extern "C" {
+#endif  // __cplusplus
+
 #if CONFIG_ACCOUNTING
 #include "av1/common/accounting.h"
 #endif
@@ -54,4 +58,7 @@
 void ifd_clear(insp_frame_data *fd);
 int ifd_inspect(insp_frame_data *fd, void *decoder);
 
-#endif
+#ifdef __cplusplus
+}  // extern "C"
+#endif  // __cplusplus
+#endif  // AOM_INSPECTION_H_