Why metal.gl traces displayed when use a CAEAGLLayer?

Our application is used a CAEAGLLayer to render, but some "metal.gl" traces seems to be displayed with instruments, as the link shown. Therefore, what's the mean of "metal.gl"?


https://user-images.githubusercontent.com/4476512/72208740-65e4c980-34e1-11ea-8e9f-3d87129ed154.png


Besides, there are many "blocked waiting for next drawable" events, and these events seems should be displayed when used a CAMetalLayer, but why displayed when used a CAEAGLLayer?


Thanks!