LayoutTests/fast/layoutformattingcontext/anonymous-inline-container-simple.html

<!-- webkit-test-runner [ LayoutFormattingContextEnabled=true LayoutFormattingContextIntegrationEnabled=false ] -->
<style>
div::first-letter {
    color: green;
}
div {
    text-rendering: optimizeSpeed;
}
</style>
<div>text content</div>