Revert "Delete SkGaussianEdgeShader"

This reverts commit 64790a3714467300848971aa153aca8cea91cf7b.

Reason for revert: pending Android fix merge.

Original change's description:
> Delete SkGaussianEdgeShader
> 
> No longer used.
> 
> Change-Id: I65a61696060ca19f528066ea587e140798450e36
> Reviewed-on: https://skia-review.googlesource.com/18132
> Reviewed-by: Jim Van Verth <jvanverth@google.com>
> Commit-Queue: Florin Malita <fmalita@chromium.org>
> 

TBR=jvanverth@google.com,fmalita@chromium.org,reed@google.com
No-Presubmit: true
No-Tree-Checks: true
No-Try: true

Change-Id: I88a428e942c78b1fc8e70501ba7fdda5727b2ab2
Reviewed-on: https://skia-review.googlesource.com/18156
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
10 files changed