google style guide include guards

Change-Id: I2c252f3ddcc99e96c1f5d3dab8bcb25a2a3637ea
diff --git a/vp9/common/vp9_common.h b/vp9/common/vp9_common.h
index 64804e1..893a3f8 100644
--- a/vp9/common/vp9_common.h
+++ b/vp9/common/vp9_common.h
@@ -9,8 +9,8 @@
  */
 
 
-#ifndef common_h
-#define common_h 1
+#ifndef VP9_COMMON_VP9_COMMON_H_
+#define VP9_COMMON_VP9_COMMON_H_
 
 #include <assert.h>
 #include "vpx_config.h"