6e3c04314 Synthesize buttons for embedders (flutter/engine#8873) (#32508)

https://github.com/flutter/engine/compare/3822aeccd93f...6e3c0431410c

git log 3822aeccd93f41ad96e7af0fc68ff141f7ce6f78..6e3c0431410ce3ae1e1ee7cf8c139fefd34a6cde --no-merges --oneline
6e3c04314 Synthesize buttons for embedders (flutter/engine#8873)

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