Update starboard media header description

This PR updates the description in drm.h, decode_target.h, media.h, and player.h.

b/326450058

starboard/drm.h

@@ -48,13 +48,13 @@ typedef enum SbDrmStatus {
   kSbDrmStatusNotSupportedError,
   kSbDrmStatusInvalidStateError,
   kSbDrmStatusQuotaExceededError,
-  // The following error can be used when the error status cannot be mapped to
-  // one of the above errors.
+  // The unknown error can be used when the error status cannot be mapped to
+  // one of the rest errors.
   kSbDrmStatusUnknownError,
 } SbDrmStatus;
 
 // Status of a particular media key.
-// https://w3c.github.io/encrypted-media/#idl-def-MediaKeyStatus
+// https://www.w3.org/TR/encrypted-media/#idl-def-mediakeystatus
 typedef enum SbDrmKeyStatus {
   kSbDrmKeyStatusUsable,
   kSbDrmKeyStatusExpired,
@@ -180,8 +180,14 @@ typedef void (*SbDrmSessionUpdatedFunc)(SbDrmSystem drm_system,
                                         int session_id_size);
 
 // A callback for notifications that the status of one or more keys in a session
-// has been changed.  All keys of the session and their new status will be
-// passed along.  Any keys not in the list is considered as deleted.
+// has been changed.  All keys |key_ids| of the session and their new status
+// will be passed along.  Any keys not in the list are considered as deleted.
+//
+// |number_of_keys| is the number of keys.
+//
+// |key_ids| is a pointer of a vector contains keys.
+//
+// |key_statuses| is a pointer of a vector contains the status of each key.
 typedef void (*SbDrmSessionKeyStatusesChangedFunc)(
     SbDrmSystem drm_system,
     void* context,
@@ -191,7 +197,7 @@ typedef void (*SbDrmSessionKeyStatusesChangedFunc)(
     const SbDrmKeyId* key_ids,
     const SbDrmKeyStatus* key_statuses);
 
-// A callback for signalling that a session has been closed by the SbDrmSystem
+// A callback for signalling that a session has been closed by the SbDrmSystem.
 typedef void (*SbDrmSessionClosedFunc)(SbDrmSystem drm_system,
                                        void* context,
                                        const void* session_id,
@@ -294,9 +300,11 @@ SB_EXPORT SbDrmSystem SbDrmCreateSystem(
 // used.
 //
 // |type|: The case-sensitive type of the session update request payload. Must
-//   not be NULL.
+// not be NULL.
+//
 // |initialization_data|: The data for which the session update
-//   request payload is created. Must not be NULL.
+// request payload is created. Must not be NULL.
+//
 // |initialization_data_size|: The size of the session update request payload.
 SB_EXPORT void SbDrmGenerateSessionUpdateRequest(
     SbDrmSystem drm_system,