Fix validation, stream window update edge triggering

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

@@ -385,25 +385,28 @@ static grpc_error *update_incoming_window(grpc_exec_ctx *exec_ctx,
     grpc_chttp2_initiate_write(exec_ctx, t, false, "flow_control");
   }
 
-  if (s != NULL) {
-    if (incoming_frame_size >
-        s->incoming_window_delta +
-            t->settings[GRPC_ACKED_SETTINGS]
-                       [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE]) {
-      char *msg;
-      gpr_asprintf(&msg,
-                   "frame of size %d overflows incoming window of %" PRId64,
-                   t->incoming_frame_size,
-                   s->incoming_window_delta +
-                       t->settings[GRPC_ACKED_SETTINGS]
-                                  [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE]);
-      grpc_error *err = GRPC_ERROR_CREATE(msg);
-      gpr_free(msg);
-      return err;
-    }
+  if (incoming_frame_size >
+      s->incoming_window_delta +
+          t->settings[GRPC_ACKED_SETTINGS]
+                     [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE]) {
+    char *msg;
+    gpr_asprintf(&msg, "frame of size %d overflows incoming window of %" PRId64,
+                 t->incoming_frame_size,
+                 s->incoming_window_delta +
+                     t->settings[GRPC_ACKED_SETTINGS]
+                                [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE]);
+    grpc_error *err = GRPC_ERROR_CREATE(msg);
+    gpr_free(msg);
+    return err;
+  }
 
+  if (s != NULL) {
     GRPC_CHTTP2_FLOW_DEBIT_STREAM("parse", t, s, incoming_window_delta,
                                   incoming_frame_size);
+    if (s->incoming_window_delta < -target_incoming_window / 2) {
+      grpc_chttp2_become_writable(exec_ctx, t, s, false,
+                                  "window-update-required");
+    }
     s->received_bytes += incoming_frame_size;
   }