KhronosGroup/WebGL — pull request #785 by Oletus (2014-11-12 16:42:46+00:00)
Title: Remove compound assignment restrictions from WEBGL_debug_shader_precision

It is possible to fully emulate precision for compound assignment by
replacing compound assignments with calls to the following kind of a
function:

float webgl_compound_add(inout float x, in float y) {
x = round_float(x + y);
return x;
}