This was due to FloatingToolbar using <Button> for its layouts in API 23-25, which got automatically inflated to <MaterialButton> via the custom view inflater in MDC themes. However, the default MaterialButton styling (especially backgroundTint) was overriding the styling in the <Button>, resulting in a broken FloatingToolbar. This issue was not encountered on API 24/25 since there were likely theme/style changes in those versions that override this Button. From API 26 onwards, FloatingToolbar uses a TextView and ImageView instead of Button.
PiperOrigin-RevId: 213517896
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