Sync the MutationObserver and MutationRecord interfaces with the spec

Making previousSibling and nextSibling nullable does not change the
generated code.

BUG=460722

Review URL: https://codereview.chromium.org/971573002

git-svn-id: svn://svn.chromium.org/blink/trunk@191058 bbb929c8-8fbe-4397-9dbb-9b2b20218538
2 files changed
tree: f7fa6252e26dcc709fc176504818084a3bff12c7
  1. third_party/