Calling ClientWebGLContext::UniformData() many times causes the
command buffer to fill up and we spend a fair amount of time flushing
the old buffer and allocating a new one, as well as serializing the
values.
The uniforms themselves are very small but they add up over a large
number of calls. We already have some code to track whether the
uniform values are dirty to avoid some redundancy, but a) this doesn't
cover every uniform, and b) we invalidate them all when switching
program.
This patch makes us track the value of every uniform that gets set
dynamically, and tracks the values separately for each program
used. It then uses these to avoid calling UniformData redundantly.
Differential Revision: https://phabricator.services.mozilla.com/D190269
836b0d935c