WebGL Gl_FragColor Alpha Behave Differently In Chrome With Firefox

Code below draws three triangles alpha value 0.5 with {premultipliedAlpha: false}. Result in Chrome: Result in Firefox: The result in Firefox is what I expected. I think it's no

Solution 1:

Anser this question myself.

As @gman said in the comment area, this is a bug in chromium.
Here is the bug link(thanks to @gman again).