The following test fails on GTK since r231440-231449: fast/canvas/webgl/index-validation-with-subsequent-draws.html CONSOLE MESSAGE: line 50: WebGL: INVALID_OPERATION: drawElements: unable to simulate vertexAttrib0 array CONSOLE MESSAGE: line 56: WebGL: INVALID_OPERATION: drawElements: unable to simulate vertexAttrib0 array Interestingly, in debug it times out instead of failing, but the error message is still there.
Fixed by r258875.