Change metadata type from uint8_t to uint32_t.

The metadata_type syntax element in the bitstream is of the type leb128(),
which can be from 0 to 1^32 - 1. It would be good to declare the
metadata type field or function parameter as uint32_t to be
future-proof.

Also declare the "uint8_t *data" parameter of aom_img_add_metadata() and
aom_img_metadata_alloc() as const.

BUG=aomedia:2507

Change-Id: If00379639119788da04bfc9cd56a3980314db742

aom/aom_image.h

diff --git a/aom/aom_image.h b/aom/aom_image.h
index d07d485..7f6c916 100644
--- a/aom/aom_image.h
+++ b/aom/aom_image.h
@@ -142,7 +142,7 @@
 
 /*!\brief Metadata payload. */
 typedef struct aom_metadata {
-  uint8_t type;     /**< Metadata type */
+  uint32_t type;    /**< Metadata type */
   uint8_t *payload; /**< Metadata payload data */
   size_t sz;        /**< Metadata payload size */
 } aom_metadata_t;
@@ -347,7 +347,7 @@
  * \param[in]    data      Metadata contents
  * \param[in]    sz        Metadata contents size
  */
-int aom_img_add_metadata(aom_image_t *img, uint8_t type, uint8_t *data,
+int aom_img_add_metadata(aom_image_t *img, uint32_t type, const uint8_t *data,
                          size_t sz);
 
 /*!\brief Remove metadata from image.
@@ -373,7 +373,8 @@
  * \param[in]    data      Metadata data pointer
  * \param[in]    sz        Metadata size
  */
-aom_metadata_t *aom_img_metadata_alloc(uint8_t type, uint8_t *data, size_t sz);
+aom_metadata_t *aom_img_metadata_alloc(uint32_t type, const uint8_t *data,
+                                       size_t sz);
 
 /*!\brief Free metadata struct.
  *

aom/src/aom_image.c

diff --git a/aom/src/aom_image.c b/aom/src/aom_image.c
index 9f7ed99..2148253 100644
--- a/aom/src/aom_image.c
+++ b/aom/src/aom_image.c
@@ -288,7 +288,8 @@
     return img->d_h;
 }
 
-aom_metadata_t *aom_img_metadata_alloc(uint8_t type, uint8_t *data, size_t sz) {
+aom_metadata_t *aom_img_metadata_alloc(uint32_t type, const uint8_t *data,
+                                       size_t sz) {
   aom_metadata_t *metadata =
       (aom_metadata_t *)calloc(1, sizeof(aom_metadata_t));
   if (!metadata) return NULL;
@@ -345,7 +346,7 @@
   return deleted_metadatas;
 }
 
-int aom_img_add_metadata(aom_image_t *img, uint8_t type, uint8_t *data,
+int aom_img_add_metadata(aom_image_t *img, uint32_t type, const uint8_t *data,
                          size_t sz) {
   if (!img) return -1;
   if (!img->metadata) {