Resolving multisample rendertargets

Hey guys,
I might be missing something obvious, but how do you resolve multisample rendertargets if you want to read from them in a next step? I would use glBlitFramebuffer, but that does not seem to be exposed?

You render to them, then they are available to be bound as inputs to later shaders.

renderer.setRenderTarget( yourTarget );
myShader.uniforms.myInputRenderTarget.value = renderTarget.texture