Fixed access to `constraint_flags` array in ParseHEVCCodecId function.

media/base/video_codecs.cc

Index: media/base/video_codecs.cc
diff --git a/media/base/video_codecs.cc b/media/base/video_codecs.cc
index 13afa406b4781455b4c33d2a08d0ccf7580f19a7..f60cbd6649de00993c398569fda5b270614e2b58 100644
--- a/media/base/video_codecs.cc
+++ b/media/base/video_codecs.cc
@@ -278,7 +278,7 @@ bool ParseHEVCCodecId(const std::string& codec_id,
       DVLOG(4) << __func__ << ": invalid constraint byte=" << elem[i];
       return false;
     }
-    constraint_flags[i] = constr_byte;
+    constraint_flags[i - 4] = constr_byte;
   }
 
   return true;