Currently, the skia-generated textures used for WebVR warnings are rendered once, on VR startup.

In the v0 browser UI, textures such as buttons and the URL bar must (at times) be updated between frames.  For example, when the page URL changes, a new texture must be rendered.

The current plan is to do all texture rendering via SW/raster rather than GL-backed canvases.  This means there is CPU-side overhead in updating textures, and pushing the updates to the GPU.  Gut feeling is that these won't be heavy operations, but we should verify this.