Just tried on my Nexus 5x with Chrome M67 and it's playing fine. I don't have M66 to test with since M67 is already in stable channel.

nonononoki: If you can still repro this, could you please attach the log in chrome://media-internals? That'll give us some idea why this is not playing. Thanks!

{
  "6:0": {
    "id": "6:0",
    "properties": {
      "render_id": 6,
      "player_id": 0,
      "origin_url": "https://mobile.twitter.com/",
      "frame_url": "https://mobile.twitter.com/ScottFrazier19/status/1006611940884480001/video/1",
      "frame_title": "Twitter",
      "url": "https://video.twimg.com/ext_tw_video/1006547507269300224/pu/vid/480x480/BgALXRWvDTIhcC08.mp4?tag=3",
      "total_bytes": 3276885,
      "streaming": false,
      "single_origin": true,
      "passed_cors_access_check": false,
      "range_header_supported": true,
      "pipeline_state": "kStopped",
      "info": "FFmpegDemuxer: skipping invalid or unsupported audio track",
      "debug": "Warning, FFmpegDemuxer failed to create a valid audio decoder configuration from muxed stream",
      "bitrate": 433892,
      "found_audio_stream": false,
      "found_video_stream": true,
      "height": 480,
      "max_duration": 60.418322,
      "start_time": 0,
      "time_base": "1/15360",
      "video_codec_name": "h264",
      "video_format": "PIXEL_FORMAT_I420",
      "video_is_encrypted": false,
      "width": 480,
      "error": "video decoder initialization failed",
      "pipeline_error": "DECODER_ERROR_NOT_SUPPORTED",
      "event": "WEBMEDIAPLAYER_DESTROYED",
      "duration": 60.418322
    },
    "allEvents": [
      {
        "time": 0,
        "key": "origin_url",
        "value": "https://mobile.twitter.com/"
      },
      {
        "time": 0.04499995708465576,
        "key": "frame_url",
        "value": "https://mobile.twitter.com/ScottFrazier19/status/1006611940884480001/video/1"
      },
      {
        "time": 0.059999942779541016,
        "key": "frame_title",
        "value": "Twitter"
      },
      {
        "time": 0.43899989128112793,
        "key": "url",
        "value": "https://video.twimg.com/ext_tw_video/1006547507269300224/pu/vid/480x480/BgALXRWvDTIhcC08.mp4?tag=3"
      },
      {
        "time": 814.6710000038147,
        "key": "total_bytes",
        "value": 3276885
      },
      {
        "time": 814.7119998931885,
        "key": "streaming",
        "value": false
      },
      {
        "time": 814.7249999046326,
        "key": "single_origin",
        "value": true
      },
      {
        "time": 814.7369999885559,
        "key": "passed_cors_access_check",
        "value": false
      },
      {
        "time": 814.74899995327,
        "key": "range_header_supported",
        "value": true
      },
      {
        "time": 815.5369999408722,
        "key": "pipeline_state",
        "value": "kStarting"
      },
      {
        "time": 865.4670000076294,
        "key": "info",
        "value": "FFmpegDemuxer: created video stream, config codec: h264 format: 1 profile: h264 baseline coded size: [480,480] visible rect: [0,0,480,480] natural size: [480,480] has extra data? true encryption scheme: Unencrypted rotation: 0°"
      },
      {
        "time": 865.9109998941422,
        "key": "debug",
        "value": "Warning, FFmpegDemuxer failed to create a valid audio decoder configuration from muxed stream"
      },
      {
        "time": 865.9389998912811,
        "key": "info",
        "value": "FFmpegDemuxer: skipping invalid or unsupported audio track"
      },
      {
        "time": 866.1269999742508,
        "key": "bitrate",
        "value": 433892
      },
      {
        "time": 866.1269999742508,
        "key": "found_audio_stream",
        "value": false
      },
      {
        "time": 866.1269999742508,
        "key": "found_video_stream",
        "value": true
      },
      {
        "time": 866.1269999742508,
        "key": "height",
        "value": 480
      },
      {
        "time": 866.1269999742508,
        "key": "max_duration",
        "value": 60.418322
      },
      {
        "time": 866.1269999742508,
        "key": "start_time",
        "value": 0
      },
      {
        "time": 866.1269999742508,
        "key": "time_base",
        "value": "1/15360"
      },
      {
        "time": 866.1269999742508,
        "key": "video_codec_name",
        "value": "h264"
      },
      {
        "time": 866.1269999742508,
        "key": "video_format",
        "value": "PIXEL_FORMAT_I420"
      },
      {
        "time": 866.1269999742508,
        "key": "video_is_encrypted",
        "value": false
      },
      {
        "time": 866.1269999742508,
        "key": "width",
        "value": 480
      },
      {
        "time": 866.6389999389648,
        "key": "error",
        "value": "video decoder initialization failed"
      },
      {
        "time": 876.5369999408722,
        "key": "pipeline_error",
        "value": "DECODER_ERROR_NOT_SUPPORTED"
      },
      {
        "time": 878.2259999513626,
        "key": "pipeline_state",
        "value": "kStopping"
      },
      {
        "time": 878.4399999380112,
        "key": "pipeline_state",
        "value": "kStopped"
      },
      {
        "time": 886.8549998998642,
        "key": "event",
        "value": "WEBMEDIAPLAYER_DESTROYED"
      },
      {
        "time": 866.0219999551773,
        "key": "duration",
        "value": 60.418322
      }
    ],
    "lastRendered": 0,
    "firstTimestamp_": 592211796.047,
    "destructed": true
  }
}

Oh, I found out why it's not working. Apparently Chromium for Android does not support H.264. Issue can be closed.

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Alright, thanks a lot for the info! Mark as WontFix.