Every text frame must inform the glyph atlas about the glyphs + scale it contains. When this happens, the glyph atlas will populate the glyph and then tell teh text frame about the location in the atlas, so that the text contents shader can sample it correctly.
Once this has been done once for a given text frame + scale + offset, we can actually just keep reusing the same data provided 1) the atlas itself hasn't changed and 2) the scale/offset/properties are the same.
This constitutes a nice CPU usage reduction in places where there is a lot of text that isn't being invalidated, like scrolling on the flutter gallery.
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