That was much tougher than expected. No wonder other WebGL video demos around the web are broken.
Firefox OpenGL / ANGLE and Chrome OpenGL were ok, getting it to work in Chrome ANGLE was rather tricky.
Please report if something got broken. I tried to go through all textured examples but I may have missed something.
If you want to refresh texture on WebGL side, you just set "texture.needsUpdate" flag (if you use Loader or ImageUtils.loadTexture / loadTextureCube everything is taken care of).
Flag has to be set also for canvas-based textures, sorry no escaping this :(. I tried and it lead to ugly problems (e.g. AO minecraft demo mixes several asynchronously loaded and generated images into one texture, with autodetect always something was broken).
"needsUpdate" should work also on cube textures, though it's not tested yet (also there I didn't put hack for Chrome ANGLE).
Mr.doob
alteredq