Do screen size calculations in vertex shader; seems to have better accuracy
Load and draw textures with premultiplied alpha
Premultiply gradient colors
[un]premultiply pixels for {get,put}imageData
Fixed WebGL to load unpremultiplied textures by default
Fixed state not updated when setting composite op
Fix font drawing when alpha != 1
Merge remote-tracking branch 'upstream/master' into text-input

Merge branch 'upstream/master' with branch 'text-input'