Set error detail if aom_codec_encode itself fails

Change-Id: I80a1934c92b38e24e96ab4dfaf0c8fb78b9434f2

aom/src/aom_encoder.c

diff --git a/aom/src/aom_encoder.c b/aom/src/aom_encoder.c
index 3b028ff..6ad6582 100644
--- a/aom/src/aom_encoder.c
+++ b/aom/src/aom_encoder.c
@@ -179,6 +179,9 @@
   else if (img && ((img->fmt & AOM_IMG_FMT_HIGHBITDEPTH) != 0) !=
                       ((ctx->init_flags & AOM_CODEC_USE_HIGHBITDEPTH) != 0)) {
     res = AOM_CODEC_INVALID_PARAM;
+    ctx->priv->err_detail =
+        "img is high bit-depth and codec was not initialized with "
+        "AOM_CODEC_USE_HIGHBITDEPTH, or vice versa.";
 #if ULONG_MAX > UINT32_MAX
   } else if (duration > UINT32_MAX) {
     res = AOM_CODEC_INVALID_PARAM;