Currently, our UI elements use textures with hardcoded sizes. Calculate a more appropriate texture size by e.g. measuring how many pixels this element cover on the screen. See the content quad element for an example how that can be done (https://cs.chromium.org/chromium/src/chrome/browser/vr/elements/content_element.cc?rcl=48ceab2955038f4754798addeb560d4955ae36e9&l=186).