Emoji rendered as all black with Cairo backend

I have a particular file, as attached, which is generated by entering an emoji in Google Doc, exporting it to PDF then cropping the page. It renders file in Acrobat and macOS Preview, but if I were to use pdftocairo this way:

pdftocairo input.pdf -pdf output.pdf

Then the output shows a black glyph instead of the intended colour glyph.

The same happens if I were to print to a Cairo context with poppler_page_render_for_printing_with_options, etc. So, I think the problem is within CairoFontEngine, possibly _render_type3_glyph?

This happens on Poppler 0.74 with Cairo 1.16, and I have verified that otherwise drawing emojis with PangoCairo works fine.

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