Comment # 8 on bug 92806 from Michel Dänzer

A num-compilations spike without a num-shaders-created spike means the shader
compile was triggered by the driver, either because UT4 used the GLSL shader
for the first time or because UT4 changed some OpenGL state affecting the code
generated for the shader.

A num-compilations spike with a num-shaders-created spike means the shader
compile was triggered by the state tracker or by UT4 itself.