Grain Effect at Comp level, not Layer

[MikeSevigny]

Request:
An option in the Add Grain effect that would add the grain at the Composition level rather than having the grain move and distort with the layer it's applied to. The result would be grain that ignores the layer's tranforms but uses the layer's (transformed & effected) alpha channel as a matte, whether the layer is 2D or 3D.

Current Workaround:

1.  Create a new Adjustment Layer with Add Grain above the target layer
2.  Select the target layer as an alpha matte for the new Adjustment Layer
3.  Repeat for each layer that requires grain

Add Grain is typically used to match the existing grain of the footage layer underneath the layer being composited. For me, the above would be the default option.