The debug surface view's output surface can become invalid during a transformation due to the parent activity pausing, for example. This can currently cause a crash when backing out of the `TransformerActivity` in the demo because the surface can be destroyed before the transformer has fully canceled.
Also clarify naming of the outputSurface and inline the private method that created `EGLSurface`s (it was shorter after removing the debug preview).
PiperOrigin-RevId: 449963440
