resolvesGlyphOutlines

True when this canvas needs resolved glyph outlines (TextGlyph.outline), i.e. it actually paints (a render backend). Extraction canvases that only read text + advances override this to false, letting the driver skip the cost of resolving glyph outlines. Such a canvas gets every text run through drawGlyphs, also a run that paints nothing, such as invisible OCR text.