By removing type slice, renaming type sliceStruct to type slice and
whacking until it compiles.

Has a pleasing net reduction of conversions.

Fixes #10188

Change-Id: I77202b8df637185b632fd7875a1fdd8d52c7a83c
Reviewed-on: https://go-review.googlesource.com/8770Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>