Allow sending preformatted messages

src/core/channel/call_op_string.c

@@ -112,6 +112,9 @@ char *grpc_call_op_string(grpc_call_op *op) {
     case GRPC_SEND_MESSAGE:
       bprintf(&b, "SEND_MESSAGE");
       break;
+    case GRPC_SEND_PREFORMATTED_MESSAGE:
+      bprintf(&b, "SEND_PREFORMATTED_MESSAGE");
+      break;
     case GRPC_SEND_FINISH:
       bprintf(&b, "SEND_FINISH");
       break;

src/core/channel/channel_stack.h

@@ -69,6 +69,8 @@ typedef enum {
   GRPC_SEND_START,
   /* send a message to the channels peer */
   GRPC_SEND_MESSAGE,
+  /* send a pre-formatted message to the channels peer */
+  GRPC_SEND_PREFORMATTED_MESSAGE,
   /* send half-close to the channels peer */
   GRPC_SEND_FINISH,
   /* request that more data be allowed through flow control */

src/core/channel/connected_channel.c

@@ -140,6 +140,8 @@ static void call_op(grpc_call_element *elem, grpc_call_element *from_elem,
       grpc_sopb_add_begin_message(&calld->outgoing_sopb,
                                   grpc_byte_buffer_length(op->data.message),
                                   op->flags);
+      /* fall-through */
+    case GRPC_SEND_PREFORMATTED_MESSAGE:
       copy_byte_buffer_to_stream_ops(op->data.message, &calld->outgoing_sopb);
       calld->outgoing_buffer_length_estimate +=
           (5 + grpc_byte_buffer_length(op->data.message));