The 'GPU shader processing' is a profiling category available for both in the 'Process' and 'System'
What's the difference? The metrics are different. For example, for a game I'm profiling, the
Process->GPU shader processing
% Time Shading Vertex is 30
% Time Shading Fragment is 70
where as
System->GPU shader processing
% Time Shading Vertex is 55
% Time Shading Fragment is 45