Cesium: Firefox WebGL warnings in console

[thw0rted]

When I load the basic viewer in Firefox (56.0, 64-bit, Ubuntu 16.04), I see repeated errors in the console:

Error: WebGL warning: texImage2D: Alpha-premult and y-flip are deprecated for non-DOM-Element uploads.

When I try to work with billboards, I also see

Error: WebGL warning: texSubImage2D: Texture has not been initialized prior to a partial upload, forcing the browser to clear it. This may be slow.

and

Error: WebGL warning: texSubImage2D: This operation requires zeroing texture data. This is slow.

In my (much more complex) application, I get tons of these warnings, until Firefox just gives up and stops warning. I don't know if this is actually having a performance impact; Chromium does do a few FPS better than Firefox but that could be for other reasons.

(I have seen #1317 but if you click through to the Bugzilla link, they think that issue has been fixed, and would only account for one of the 3 warning types.)

[hpinkos]

Thanks @thw0rted! I see this on my windows machine as well.

@lilleyse do you know what this might be from?

[pjcozzi]

Good catch, thanks @thw0rted!

I suspect a new version WebGL 1.0.x version make these deprecations:

Error: WebGL warning: texImage2D: Alpha-premult and y-flip are deprecated for non-DOM-Element uploads.

The other errors are like due to not calling texImage2D before texSubImage2D - which Cesium _should_ do everywhere.

@bagnell do you want to look at this since @lilleyse has his hands full with your PRs. :)