Make animated image playback speed match browser (Firefox and Chrome) behaviour

[goldbattle]

Pull request checklist:

• CHANGELOG.md was updated, if applicable

Description

Animated emotes can have very fast animation compared to the twitch web viewer. This is caused by the browser enforcing a minimum frame time. For example an emote could be animated in chatterino at 1ms per frame, but in any web browser the actual framerate is 100ms for frame. I think most people would expect emotes the behave like in the browser. See this issue for some background: SevenTV#46

Details on how browsers implement it are here:
https://source.chromium.org/chromium/chromium/src/+/fe1bca993584d616f52d9088d6b1411537441e9d:third_party/blink/renderer/platform/graphics/deferred_image_decoder.cc;l=353-360;bpv=1;bpt=0
https://bugzilla.mozilla.org/show_bug.cgi?id=1511298#c7

base::TimeDelta DeferredImageDecoder::FrameDurationAtIndex(size_t index) const {
  base::TimeDelta duration;
  if (metadata_decoder_)
    duration = metadata_decoder_->FrameDurationAtIndex(index);
  if (index < frame_data_.size())
    duration = frame_data_[index].duration_;
  // Many annoying ads specify a 0 duration to make an image flash as quickly as
  // possible. We follow Firefox's behavior and use a duration of 100 ms for any
  // frames that specify a duration of <= 10 ms. See <rdar://problem/7689300>
  // and <http://webkit.org/b/36082> for more information.
  if (duration <= base::TimeDelta::FromMilliseconds(10))
    duration = base::TimeDelta::FromMilliseconds(100);
  return duration;
}

[Felanbird]

I don't have this issue so I'm not sure if this fixes it, but both PR's will need a Changelog entry either way.

[jupjohn]

SevenTV#46 is is actually caused by missing frames, unrelated :)

[pajlada]

Thanks for your contribution! As a first-time contributor, you can now add yourself to the contributors list that's shown inside the application.

To do so, open a new PR where you modify the resources/contributors.txt file and add yourself to the list. Make sure to read the comments at a top for instructions.