added some more docs

src/core/ext/load_reporting/load_reporting.h

@@ -58,8 +58,11 @@ typedef enum grpc_load_reporting_source {
 typedef struct grpc_load_reporting_call_data {
   const grpc_load_reporting_source source; /**< point of last data update. */
 
-  // XXX
+  /** Unique identifier for the channel associated with the data */
   intptr_t channel_id;
+
+  /** Unique identifier for the call associated with the data. If the call
+   * hasn't been created yet, it'll have a value of zero. */
   intptr_t call_id;
 
   /** Only valid when \a source is \a GRPC_LR_POINT_CALL_DESTRUCTION, that is,

src/core/ext/transport/chttp2/transport/writing.c

@@ -264,6 +264,7 @@ static void finalize_outbuf(grpc_exec_ctx *exec_ctx,
             send_bytes, is_last_frame, &stream_writing->stats,
             &transport_writing->outbuf);
         if (is_first_data_frame) {
+          /* TODO(dgq): this is a hack. It'll be fix in a future refactoring */
           stream_writing->stats.data_bytes -= 5; /* discount grpc framing */
           is_first_data_frame = false;
         }