Remove SkImageFilter::MakeBlur entry point

AFAICT none of our clients use this entry point and it is tangling up efforts to add a new parameter to the BlurImageFilter.

Change-Id: I494634db98a1d246854a5e3735380fbe55f425c2
Reviewed-on: https://skia-review.googlesource.com/20837
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
5 files changed