Description:
Fresh install, no user extensions. Multiple Opera-bundled extensions fail content verification:

ERROR:content_hash.cc:267 Fetching verified_contents.json failed
  for extension ddfjocfgcmcbeejfjefghoegecamfbof version 2.0 (error -300)
ERROR:content_hash.cc:267 Fetching verified_contents.json failed
  for extension eaahgnceaiheanheajmiojafolhdfbih version 1.5 (error -300)
ERROR:content_hash.cc:267 Fetching verified_contents.json failed
  for extension fbjgnhgkjlcbbmdflhhegadcjmmlnlfp version 1.0.6 (error -300)

Followed by multiple verification failures for files in extension ddfjocfgcmcbeejfjefghoegecamfbof (GX wallpaper/modding):

Content verify job failed at path: webmodding/opera.css
Content verify job failed at path: wallpaper/My Movie 48.webm

Error -300 indicates a fetch/network failure for Opera's own bundled extensions.